description: You are given two integers l and r, l≤ r. Find the largest possible value of a mod b over all pairs (a, b) of integers for which r≥ a ≥ b ≥ l.
  
  As a reminder, a mod b is a remainder we get when dividing a by b. For example, 26 mod 8 = 2.
  
  Input
  
  Each test contains multiple test cases.
  
  The first line contains one positive integer t (1≤ t≤ 10^4), denoting the number of test cases. Description of the test cases follows.
  
  The only line of each test case contains two integers l, r (1≤ l ≤ r ≤ 10^9).
  
  Output
  
  For every test case, output the largest possible value of a mod b over all pairs (a, b) of integers for which r≥ a ≥ b ≥ l.
  
  Example
  
  Input
  
  
  4
  1 1
  999999999 1000000000
  8 26
  1 999999999
  
  
  Output
  
  
  0
  1
  12
  499999999
  
  Note
  
  In the first test case, the only allowed pair is (a, b) = (1, 1), for which a mod b = 1 mod 1 = 0.
  
  In the second test case, the optimal choice is pair (a, b) = (1000000000, 999999999), for which a mod b = 1.
solution: import java.io.*;
  import java.util.*;
   
  public class _1562a {
      FastScanner scn;
      PrintWriter w;
      PrintStream fs;
  
      long MOD = 1000000007;
      int N=100000+10;
      long mul(long x, long y) {long res = x * y; return (res >= MOD ? res % MOD : res);}
      long power(long x, long y) {if (y < 0) return 1; long res = 1; x %= MOD; while (y!=0) {if ((y & 1)==1)res = mul(res, x); y >>= 1; x = mul(x, x);} return res;}
      void ruffleSort(int[] a) {int n=a.length;Random r=new Random();for (int i=0; i<a.length; i++) {int oi=r.nextInt(n), temp=a[i];a[i]=a[oi];a[oi]=temp;}Arrays.sort(a);}
      boolean LOCAL;
      void debug(Object... o){if(LOCAL)System.err.println(Arrays.deepToString(o));}
      
      void solve(){
  
          int t=scn.nextInt();
              while(t-->0)
              {
                     long a=scn.nextLong(),b=scn.nextLong();
                     if(a>b){
                          long v=a;
                          a=b;
                          b=v;
                     }
                     long s=b/2+1;
                     if(s>=a&&s<=b){
                          w.println(b%s);
                     }else{
                         w.println(b%a);
                     }
              
              
              }
          
      }
   
      void run() {
          try {
              long ct = System.currentTimeMillis();
              scn = new FastScanner(new File("input.txt"));
              w = new PrintWriter(new File("output.txt"));
              fs=new PrintStream("error.txt");
              System.setErr(fs);
              LOCAL=true;
   
              solve();
   
              w.close();
              System.err.println(System.currentTimeMillis() - ct);
          } catch (FileNotFoundException e) {
              e.printStackTrace();
          }
      }
   
      void runIO() {
   
          scn = new FastScanner(System.in);
          w = new PrintWriter(System.out);
          LOCAL=false;
   
          solve();
   
          w.close();
      }
   
      class FastScanner {
          BufferedReader br;
          StringTokenizer st;
   
          public FastScanner(File f) {
              try {
                  br = new BufferedReader(new FileReader(f));
              } catch (FileNotFoundException e) {
                  e.printStackTrace();
              }
          }
   
          public FastScanner(InputStream f) {
              br = new BufferedReader(new InputStreamReader(f));
          }
   
          String next() {
              while (st == null || !st.hasMoreTokens()) {
                  String s = null;
                  try {
                      s = br.readLine();
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
                  if (s == null)
                      return null;
                  st = new StringTokenizer(s);
              }
              return st.nextToken();
          }
   
          boolean hasMoreTokens() {
              while (st == null || !st.hasMoreTokens()) {
                  String s = null;
                  try {
                      s = br.readLine();
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
                  if (s == null)
                      return false;
                  st = new StringTokenizer(s);
              }
              return true;
          }
   
          int nextInt() {
              return Integer.parseInt(next());
          }
          
          int[] nextIntArray(int n) {
              int a[] = new int[n];
              for (int i = 0; i < n; i++) {
                  a[i] = nextInt();
              }
              return a;
          }
  
          long[] nextLongArray(int n) {
              long a[] = new long[n];
              for (int i = 0; i < n; i++) {
                  a[i] = nextLong();
              }
              return a;
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
   
          double nextDouble() {
              return Double.parseDouble(next());
          }
      }
   
      public static void main(String[] args) {
          new _1562a().runIO();
      }
  }
  
  