description: This is the easy version of the problem. The only difference between the two versions is the constraint on n. You can make hacks only if all versions of the problem are solved.
  
  A forest is an undirected graph without cycles (not necessarily connected).
  
  Mocha and Diana are friends in Zhijiang, both of them have a forest with nodes numbered from 1 to n, and they would like to add edges to their forests such that: 
  
    * After adding edges, both of their graphs are still forests. 
    * They add the same edges. That is, if an edge (u, v) is added to Mocha's forest, then an edge (u, v) is added to Diana's forest, and vice versa. 
  
  
  
  Mocha and Diana want to know the maximum number of edges they can add, and which edges to add.
  
  Input
  
  The first line contains three integers n, m_1 and m_2 (1 ≤ n ≤ 1000, 0 ≤ m_1, m_2 < n) — the number of nodes and the number of initial edges in Mocha's forest and Diana's forest.
  
  Each of the next m_1 lines contains two integers u and v (1 ≤ u, v ≤ n, u ≠ v) — the edges in Mocha's forest.
  
  Each of the next m_2 lines contains two integers u and v (1 ≤ u, v ≤ n, u ≠ v) — the edges in Diana's forest.
  
  Output
  
  The first line contains only one integer h, the maximum number of edges Mocha and Diana can add (in each forest).
  
  Each of the next h lines contains two integers u and v (1 ≤ u, v ≤ n, u ≠ v) — the edge you add each time.
  
  If there are multiple correct answers, you can print any one of them.
  
  Examples
  
  Input
  
  
  3 2 2
  1 2
  2 3
  1 2
  1 3
  
  
  Output
  
  
  0
  
  
  Input
  
  
  5 3 2
  5 4
  2 1
  4 3
  4 3
  1 4
  
  
  Output
  
  
  1
  2 4
  
  
  Input
  
  
  8 1 2
  1 7
  2 6
  1 5
  
  
  Output
  
  
  5
  5 2
  2 3
  3 4
  4 7
  6 8
  
  Note
  
  In the first example, we cannot add any edge.
  
  In the second example, the initial forests are as follows.
  
  <image>
  
  We can add an edge (2, 4).
  
  <image>
solution: import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;
  import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;
  import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;
  import java.lang.reflect.Array;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;import java.security.AccessControlException;import java.util.ArrayList;
  import java.util.Arrays;import java.util.Collection;import java.util.Comparator;
  import java.util.List;import java.util.Map;import java.util.Objects;import java.util.TreeMap;
  import java.util.function.Function;import java.util.stream.Collectors;import java.util.stream.IntStream;
  import java.util.stream.LongStream;import java.util.stream.Stream;public class _p001559D1 {
  static public void main(final String[] args) throws IOException{p001559D1._main(args);}
  
  static class p001559D1 extends Solver{public p001559D1(){singleTest=true;}@Override public 
  void solve()throws IOException{int n=sc.nextInt();int m1=sc.nextInt();int m2=sc.nextInt();
  sc.nextLine();DSU dsu1=new DSU(n);for(int $i0=0;$i0<m1;$i0++){int u=sc.nextInt();
  int v=sc.nextInt();sc.nextLine();int u1=dsu1.find_set(u-1);int v1=dsu1.find_set(v
  -1);dsu1.union_sets(u1,v1);}DSU dsu2=new DSU(n);for(int $i1=0;$i1<m2;$i1++){int 
  u=sc.nextInt();int v=sc.nextInt();sc.nextLine();int u1=dsu2.find_set(u-1);int v1
  =dsu2.find_set(v-1);dsu2.union_sets(u1,v1);}int[]a1=new int[n];int[]a2=new int[n];
  for(int i=0;i<n;i++){a1[i]=dsu1.find_set(i);a2[i]=dsu2.find_set(i);}int count=Math.min(Datas.mapc(a1).size(),
  Datas.mapc(a2).size())-1;ArrayList<int[]>res=new ArrayList<>();if(res.size()<count){l:
  for(int i=0;i<n-1;i++){for(int j=i+1;j<n;j++){if(dsu1.find_set(i)!=dsu1.find_set(j)
  && dsu2.find_set(i)!=dsu2.find_set(j)){res.add(new int[]{i+1,j+1});dsu1.union_sets(i,
  j);dsu2.union_sets(i,j);if(res.size()==count){break l;}}}}}pw.println(count);if(count
  >0){res.forEach(v->pw.println(Datas.join(v)));}}static public void _main(String[]args)throws 
  IOException{new p001559D1().run();}}static class DSU{private int[]parent;private 
  int[]rank;public DSU(final int n){parent=IntStream.range(0,n).toArray();rank=new 
  int[n];}public void make_set(final int v){parent[v]=v;rank[v]=0;}public int find_set(final 
  int v){if(v==parent[v]){return v;}parent[v]=find_set(parent[v]);return parent[v];
  }public void union_sets(final int a,final int b){int a1=find_set(a);int b1=find_set(b);
  if(a1!=b1){if(rank[a1]<rank[b1]){int t=a1;a1=b1;b1=t;}parent[b1]=a1;if(rank[a1]==
  rank[b1]){++rank[a1];}}}}static class Datas{final static String SPACE=" ";public 
  static TreeMap<Integer,Integer>mapc(final int[]a){return IntStream.range(0,a.length).collect(
  ()->new TreeMap<Integer,Integer>(),(res,i)->{res.put(a[i],res.getOrDefault(a[i],
  0)+1);},Map::putAll);}public static TreeMap<Long,Integer>mapc(final long[]a){return 
  IntStream.range(0,a.length).collect(()->new TreeMap<Long,Integer>(),(res,i)->{res.put(a[i],
  res.getOrDefault(a[i],0)+1);},Map::putAll);}public static<T>TreeMap<T,Integer>mapc(final 
  T[]a,Comparator<T>cmp){return IntStream.range(0,a.length).collect(cmp!=null?()->
  new TreeMap<T,Integer>(cmp):()->new TreeMap<T,Integer>(),(res,i)->{res.put(a[i],
  res.getOrDefault(a[i],0)+1);},Map::putAll);}public static<T>TreeMap<T,Integer>mapc(final 
  T[]a){return mapc(a,null);}public static TreeMap<Integer,Integer>mapc(final IntStream 
  a){return a.collect(()->new TreeMap<Integer,Integer>(),(res,v)->{res.put(v,res.getOrDefault(v,
  0)+1);},Map::putAll);}public static TreeMap<Long,Integer>mapc(final LongStream a)
  {return a.collect(()->new TreeMap<Long,Integer>(),(res,v)->{res.put(v,res.getOrDefault(v,
  0)+1);},Map::putAll);}public static<T>TreeMap<T,Integer>mapc(final Stream<T>a,Comparator<T>
  cmp){return a.collect(cmp!=null?()->new TreeMap<T,Integer>(cmp):()->new TreeMap<T,
  Integer>(),(res,v)->{res.put(v,res.getOrDefault(v,0)+1);},Map::putAll);}public static
  <T>TreeMap<T,Integer>mapc(final Stream<T>a){return mapc(a,null);}public static<T>
  TreeMap<T,Integer>mapc(final Collection<T>a,Comparator<T>cmp){return mapc(a.stream(),
  cmp);}public static<T>TreeMap<T,Integer>mapc(final Collection<T>a){return mapc(a.stream());
  }public static TreeMap<Integer,List<Integer>>mapi(final int[]a){return IntStream.range(0,
  a.length).collect(()->new TreeMap<Integer,List<Integer>>(),(res,i)->{if(!res.containsKey(a[i]))
  {res.put(a[i],Stream.of(i).collect(Collectors.toList()));}else{res.get(a[i]).add(i);
  }},Map::putAll);}public static TreeMap<Long,List<Integer>>mapi(final long[]a){return 
  IntStream.range(0,a.length).collect(()->new TreeMap<Long,List<Integer>>(),(res,i)
  ->{if(!res.containsKey(a[i])){res.put(a[i],Stream.of(i).collect(Collectors.toList()));
  }else{res.get(a[i]).add(i);}},Map::putAll);}public static<T>TreeMap<T,List<Integer>>
  mapi(final T[]a,Comparator<T>cmp){return IntStream.range(0,a.length).collect(cmp
  !=null?()->new TreeMap<T,List<Integer>>(cmp):()->new TreeMap<T,List<Integer>>(),
  (res,i)->{if(!res.containsKey(a[i])){res.put(a[i],Stream.of(i).collect(Collectors.toList()));
  }else{res.get(a[i]).add(i);}},Map::putAll);}public static<T>TreeMap<T,List<Integer>>
  mapi(final T[]a){return mapi(a,null);}public static TreeMap<Integer,List<Integer>>
  mapi(final IntStream a){int[]i=new int[]{0};return a.collect(()->new TreeMap<Integer,
  List<Integer>>(),(res,v)->{if(!res.containsKey(v)){res.put(v,Stream.of(i[0]).collect(Collectors.toList()));
  }else{res.get(v).add(i[0]);}i[0]++;},Map::putAll);}public static TreeMap<Long,List<Integer>>
  mapi(final LongStream a){int[]i=new int[]{0};return a.collect(()->new TreeMap<Long,
  List<Integer>>(),(res,v)->{if(!res.containsKey(v)){res.put(v,Stream.of(i[0]).collect(Collectors.toList()));
  }else{res.get(v).add(i[0]);}i[0]++;},Map::putAll);}public static<T>TreeMap<T,List<Integer>>
  mapi(final Stream<T>a,Comparator<T>cmp){int[]i=new int[]{0};return a.collect(cmp
  !=null?()->new TreeMap<T,List<Integer>>(cmp):()->new TreeMap<T,List<Integer>>(),
  (res,v)->{if(!res.containsKey(v)){res.put(v,Stream.of(i[0]).collect(Collectors.toList()));
  }else{res.get(v).add(i[0]);}i[0]++;},Map::putAll);}public static<T>TreeMap<T,List<Integer>>
  mapi(final Stream<T>a){return mapi(a,null);}public static<T>TreeMap<T,List<Integer>>
  mapi(final Collection<T>a,Comparator<T>cmp){return mapi(a.stream(),cmp);}public 
  static<T>TreeMap<T,List<Integer>>mapi(final Collection<T>a){return mapi(a.stream());
  }public static List<int[]>listi(final int[]a){return IntStream.range(0,a.length).mapToObj(i
  ->new int[]{a[i],i}).collect(Collectors.toList());}public static List<long[]>listi(final 
  long[]a){return IntStream.range(0,a.length).mapToObj(i->new long[]{a[i],i}).collect(Collectors.toList());
  }public static<T>List<Pair<T,Integer>>listi(final T[]a){return IntStream.range(0,
  a.length).mapToObj(i->new Pair<T,Integer>(a[i],i)).collect(Collectors.toList());
  }public static List<int[]>listi(final IntStream a){int[]i=new int[]{0};return a.mapToObj(v
  ->new int[]{v,i[0]++}).collect(Collectors.toList());}public static List<long[]>listi(final 
  LongStream a){int[]i=new int[]{0};return a.mapToObj(v->new long[]{v,i[0]++}).collect(Collectors.toList());
  }public static<T>List<Pair<T,Integer>>listi(final Stream<T>a){int[]i=new int[]{0};
  return a.map(v->new Pair<T,Integer>(v,i[0]++)).collect(Collectors.toList());}public 
  static<T>List<Pair<T,Integer>>listi(final Collection<T>a){int[]i=new int[]{0};return 
  a.stream().map(v->new Pair<T,Integer>(v,i[0]++)).collect(Collectors.toList());}public 
  static String join(final int[]a){return Arrays.stream(a).mapToObj(Integer::toString).collect(Collectors.joining(SPACE));
  }public static String join(final long[]a){return Arrays.stream(a).mapToObj(Long::toString).collect(Collectors.joining(SPACE));
  }public static<T>String join(final T[]a){return Arrays.stream(a).map(v->Objects.toString(v)).collect(Collectors.joining(SPACE));
  }public static<T>String join(final T[]a,final Function<T,String>toString){return 
  Arrays.stream(a).map(v->toString.apply(v)).collect(Collectors.joining(SPACE));}public 
  static<T>String join(final Collection<T>a){return a.stream().map(v->Objects.toString(v)).collect(Collectors.joining(SPACE));
  }public static<T>String join(final Collection<T>a,final Function<T,String>toString)
  {return a.stream().map(v->toString.apply(v)).collect(Collectors.joining(SPACE));
  }public static<T>String join(final Stream<T>a){return a.map(v->Objects.toString(v)).collect(Collectors.joining(SPACE));
  }public static<T>String join(final Stream<T>a,final Function<T,String>toString){
  return a.map(v->toString.apply(v)).collect(Collectors.joining(SPACE));}public static
  <T>String join(final IntStream a){return a.mapToObj(Integer::toString).collect(Collectors.joining(SPACE));
  }public static<T>String join(final LongStream a){return a.mapToObj(Long::toString).collect(Collectors.joining(SPACE));
  }public static List<Integer>list(final int[]a){return Arrays.stream(a).mapToObj(Integer::valueOf).collect(Collectors.toList());
  }public static List<Integer>list(final IntStream a){return a.mapToObj(Integer::valueOf).collect(Collectors.toList());
  }public static List<Long>list(final long[]a){return Arrays.stream(a).mapToObj(Long::valueOf).collect(Collectors.toList());
  }public static List<Long>list(final LongStream a){return a.mapToObj(Long::valueOf).collect(Collectors.toList());
  }public static<T>List<T>list(final Stream<T>a){return a.collect(Collectors.toList());
  }public static<T>List<T>list(final Collection<T>a){return a.stream().collect(Collectors.toList());
  }public static<T>List<T>list(final T[]a){return Arrays.stream(a).collect(Collectors.toList());
  }public static String yesNo(final boolean res){return res?"YES":"NO";}public static 
  String dump(Object obj){String res="";if(obj!=null){Class cl=obj.getClass();String 
  cls=cl.getName();if(cls.startsWith("[")){res+="[";for(int i=0;;i++){try{Object o
  =Array.get(obj,i);String s=dump(o);if(i>0){res+=", ";}res+=s;}catch(ArrayIndexOutOfBoundsException 
  ex){break;}}res+="]";}else if(Collection.class.isAssignableFrom(cl)){@SuppressWarnings("unchecked")final 
  Object s=((Collection)obj).stream().map(v->dump(v)).collect(Collectors.joining(", ",
  "[","]"));res+=s.toString();}else if(Map.class.isAssignableFrom(cl)){@SuppressWarnings("unchecked")final 
  Object s=((Map)obj).entrySet().stream().map(v->dump(v)).collect(Collectors.joining(", ",
  "{","}"));res+=s.toString();}else if(Character.class.isInstance(obj)|| Integer.class.isInstance(obj)
  || Long.class.isInstance(obj)|| Float.class.isInstance(obj)|| Double.class.isInstance(obj)|| String.class.isInstance(obj)
  ){res+=Objects.toString(obj);}else if(Map.Entry.class.isInstance(obj)){res+=dump(((Map.Entry)obj).getKey())
  +"="+dump(((Map.Entry)obj).getValue());}else if(Stream.class.isInstance(obj)){@SuppressWarnings("unchecked")
  final Object s=((Stream)obj).map(v->dump(v)).collect(Collectors.joining(", ","[",
  "]"));res+=s.toString();}else{res+=Stream.concat(Arrays.stream(obj.getClass().getFields()).map(v
  ->{String name=v.getName();String val;try{Object o=v.get(obj);if(o!=null && v.isAnnotationPresent(Dump.class))
  {Dump an=v.getAnnotation(Dump.class);Class ocl=o.getClass();val="{";for(String fn:an.fields())
  {try{Field f=ocl.getField(fn);val+=fn+"="+dump(f.get(o))+", ";}catch(NoSuchFieldException 
  nsfex){try{@SuppressWarnings("unchecked")final Method m=ocl.getMethod(fn);val+=fn+"="+dump(m.invoke(o))
  +", ";}catch(NoSuchMethodException | IllegalArgumentException | InvocationTargetException 
  nsmex){}}}if(val.endsWith(", ")){val=val.substring(0,val.length()-2);}val+="}";}
  else{val=dump(o);}}catch(IllegalAccessException ex){val="N/A";}return name+"="+val;
  }),Arrays.stream(obj.getClass().getMethods()).filter(m->m.isAnnotationPresent(Getter.class)).map(m
  ->{String name=m.getName();String val;try{Object o=m.invoke(obj);if(o!=null && m.isAnnotationPresent(Dump.class))
  {Dump an=m.getAnnotation(Dump.class);Class ocl=o.getClass();val="{";for(String fn:an.fields())
  {try{Field f=ocl.getField(fn);val+=fn+"="+dump(f.get(o))+", ";}catch(NoSuchFieldException 
  nsfex){try{@SuppressWarnings("unchecked")final Method m1=ocl.getMethod(fn);val+=fn+"="+dump(m1.invoke(o))
  +", ";}catch(NoSuchMethodException | IllegalArgumentException | InvocationTargetException 
  nsmex){}}}if(val.endsWith(", ")){val=val.substring(0,val.length()-2);}val+="}";}else
  {val=dump(o);}}catch(IllegalAccessException | InvocationTargetException ex){val=
  "N/A";}return name+"="+val;})).collect(Collectors.joining(", ","{"+obj.getClass().getName()
  +": ","}"));}}if(res.length()==0){res="<null>";}return res;}}@Retention(RetentionPolicy.RUNTIME)
  public @interface Dump{String[]fields();}@Retention(RetentionPolicy.RUNTIME)public @interface Getter{}static class 
  Pair<K,V>{private K k;private V v;public Pair(final K t,final V u){this.k=t;this.v
  =u;}public K getKey(){return k;}public V getValue(){return v;}public void setKey(K 
  t){k=t;}public void setValue(V t){v=t;}}static class MyScanner{private StringBuilder 
  cache=new StringBuilder();int cache_pos=0;private int first_linebreak=-1;private 
  int second_linebreak=-1;private StringBuilder sb=new StringBuilder();private InputStream 
  is=null;public MyScanner(final InputStream is){this.is=is;}public String charToString(final 
  int c){return String.format("'%s'",c=='\n'?"\\n":(c=='\r'?"\\r":String.valueOf((char)c)));
  }public int get(){int res=-1;if(cache_pos<cache.length()){res=cache.charAt(cache_pos);
  cache_pos++;if(cache_pos==cache.length()){cache.delete(0,cache_pos);cache_pos=0;
  }}else{try{res=is.read();}catch(IOException ex){throw new RuntimeException(ex);}
  }return res;}private void unget(final int c){if(cache_pos==0){cache.insert(0,(char)c);
  }else{cache_pos--;}}public String nextLine(){sb.delete(0,sb.length());int c;boolean 
  done=false;boolean end=false;while((c=get())!=-1){if(check_linebreak(c)){done=true;
  if(c==first_linebreak){if(!end){end=true;}else{cache.append((char)c);break;}}else 
  if(second_linebreak!=-1 && c==second_linebreak){break;}}if(end && c!=first_linebreak 
  && c!=second_linebreak){cache.append((char)c);break;}if(!done){sb.append((char)c);
  }}return!done && sb.length()==0?null:sb.toString();}private boolean check_linebreak(int 
  c){if(c=='\n'|| c=='\r'){if(first_linebreak==-1){first_linebreak=c;}else if(c!=first_linebreak 
  && second_linebreak==-1){second_linebreak=c;}return true;}return false;}public int 
  nextInt(){return Integer.parseInt(next());}public long nextLong(){return Long.parseLong(next());
  }public boolean hasNext(){boolean res=false;int c;while((c=get())!=-1){if(!check_linebreak(c)
  && c!=' '&& c!='\t'){res=true;unget(c);break;}}return res;}public String next(){
  sb.delete(0,sb.length());boolean started=false;int c;while((c=get())!=-1){if(check_linebreak(c)
  || c==' '|| c=='\t'){if(started){unget(c);break;}}else{started=true;sb.append((char)c);
  }}return sb.toString();}public int nextChar(){return get();}public boolean eof()
  {int c=get();boolean res=false;if(c!=-1){unget(c);}else{res=true;}return res;}public 
  double nextDouble(){return Double.parseDouble(next());}}static abstract class Solver
  {protected String nameIn=null;protected String nameOut=null;protected boolean singleTest
  =false;protected MyScanner sc=null;protected PrintWriter pw=null;private int current_test
  =0;private int count_tests=0;protected int currentTest(){return current_test;}protected 
  int countTests(){return count_tests;}private void process()throws IOException{if(!singleTest)
  {count_tests=sc.nextInt();sc.nextLine();for(current_test=1;current_test<=count_tests;
  current_test++){solve();pw.flush();}}else{count_tests=1;current_test=1;solve();}
  }abstract protected void solve()throws IOException;public void run()throws IOException
  {boolean done=false;try{if(nameIn!=null){if(new File(nameIn).exists()){try(FileInputStream 
  fis=new FileInputStream(nameIn);PrintWriter pw0=select_output();){select_output();
  done=true;sc=new MyScanner(fis);pw=pw0;process();}}else{throw new RuntimeException("File "
  +new File(nameIn).getAbsolutePath()+" does not exist!");}}}catch(IOException | AccessControlException 
  ex){}if(!done){try(PrintWriter pw0=select_output();){sc=new MyScanner(System.in);
  pw=pw0;process();}}}private PrintWriter select_output()throws FileNotFoundException
  {if(nameOut!=null){return new PrintWriter(nameOut);}return new PrintWriter(System.out);
  }}static abstract class Tester{static public int getRandomInt(final int min,final 
  int max){return(min+(int)Math.floor(Math.random()*(max-min+1)));}static public long 
  getRandomLong(final long min,final long max){return(min+(long)Math.floor(Math.random()
  *(max-min+1)));}static public double getRandomDouble(final double min,final double 
  maxExclusive){return(min+Math.random()*(maxExclusive-min));}abstract protected void 
  testOutput(final List<String>output_data);abstract protected void generateInput();
  abstract protected String inputDataToString();private boolean break_tester=false;
  protected void beforeTesting(){}protected void breakTester(){break_tester=true;}
  public boolean broken(){return break_tester;}}}
  