description: You are given two integers n and m. Find the \operatorname{MEX} of the sequence n ⊕ 0, n ⊕ 1, …, n ⊕ m. Here, ⊕ is the [bitwise XOR operator](https://en.wikipedia.org/wiki/Bitwise_operation#XOR).
  
  \operatorname{MEX} of the sequence of non-negative integers is the smallest non-negative integer that doesn't appear in this sequence. For example, \operatorname{MEX}(0, 1, 2, 4) = 3, and \operatorname{MEX}(1, 2021) = 0. 
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 30 000) — the number of test cases.
  
  The first and only line of each test case contains two integers n and m (0 ≤ n, m ≤ 10^9).
  
  Output
  
  For each test case, print a single integer — the answer to the problem.
  
  Example
  
  Input
  
  
  5
  3 5
  4 6
  3 2
  69 696
  123456 654321
  
  
  Output
  
  
  4
  3
  0
  640
  530866
  
  Note
  
  In the first test case, the sequence is 3 ⊕ 0, 3 ⊕ 1, 3 ⊕ 2, 3 ⊕ 3, 3 ⊕ 4, 3 ⊕ 5, or 3, 2, 1, 0, 7, 6. The smallest non-negative integer which isn't present in the sequence i. e. the \operatorname{MEX} of the sequence is 4.
  
  In the second test case, the sequence is 4 ⊕ 0, 4 ⊕ 1, 4 ⊕ 2, 4 ⊕ 3, 4 ⊕ 4, 4 ⊕ 5, 4 ⊕ 6, or 4, 5, 6, 7, 0, 1, 2. The smallest non-negative integer which isn't present in the sequence i. e. the \operatorname{MEX} of the sequence is 3.
  
  In the third test case, the sequence is 3 ⊕ 0, 3 ⊕ 1, 3 ⊕ 2, or 3, 2, 1. The smallest non-negative integer which isn't present in the sequence i. e. the \operatorname{MEX} of the sequence is 0.
solution: import java.util.*;
  import java.io.*;
  
  public class Main {
      public static void main(String args[]) {new Main().run();}
  
      FastReader in = new FastReader();
      PrintWriter out = new PrintWriter(System.out);
      void run() {
          for(int q=ni();q>0;q--)
          work();
          out.flush();
      }
      long mod=998244353;
      long gcd(long a,long b) {
          return a==0?b:gcd(b%a,a);
      }
      long inf=Long.MAX_VALUE/3;
  
      void work() {
          int n=ni(),m=ni();
          int v=0;
          for(int i=30;i>=0;i--){
              if((1<<i&n)==0&&(1<<i&m)>0){
                  v+=1<<i;
              }else if((1<<i&n)>0&&(1<<i&m)==0){
                  break;
              }
          }
          if((v^n)==m){
              for(int i=0;i<=30;i++){
                  if(((1<<i)&m)>0){
                      if(((1<<i)&v)>0){
                          v-=1<<i;
                      }
                  }else{
                      v+=1<<i;
                      break;
                  }
              }
          }
          out.println(v);
      }
  
      //input
      @SuppressWarnings("unused")
      private ArrayList<Integer>[] ng(int n, int m) {
          ArrayList<Integer>[] graph=(ArrayList<Integer>[])new ArrayList[n];
          for(int i=0;i<n;i++) {
              graph[i]=new ArrayList<>();
          }
          for(int i=1;i<=m;i++) {
              int s=in.nextInt()-1,e=in.nextInt()-1;
              graph[s].add(e);
              graph[e].add(s);
          }
          return graph;
      }
  
      private ArrayList<long[]>[] ngw(int n, int m) {
          ArrayList<long[]>[] graph=(ArrayList<long[]>[])new ArrayList[n];
          for(int i=0;i<n;i++) {
              graph[i]=new ArrayList<>();
          }
          for(int i=1;i<=m;i++) {
              long s=in.nextLong()-1,e=in.nextLong()-1,w=in.nextLong();
              graph[(int)s].add(new long[] {e,w});
              graph[(int)e].add(new long[] {s,w});
          }
          return graph;
      }
  
      private int ni() {
          return in.nextInt();
      }
  
      private long nl() {
          return in.nextLong();
      }
      private double nd() {
          return in.nextDouble();
      }
      private String ns() {
          return in.next();
      }
  
      private long[] na(int n) {
          long[] A=new long[n];
          for(int i=0;i<n;i++) {
              A[i]=in.nextLong();
          }
          return A;
      }
  
      private int[] nia(int n) {
          int[] A=new int[n];
          for(int i=0;i<n;i++) {
              A[i]=in.nextInt();
          }
          return A;
      }
  }
  
  class FastReader
  {
      BufferedReader br;
      StringTokenizer st;
      InputStreamReader input;//no buffer
      public FastReader()
      {
          br=new BufferedReader(new InputStreamReader(System.in));
      }
  
      public FastReader(boolean isBuffer)
      {
          if(!isBuffer){
              input=new InputStreamReader(System.in);
          }else{
              br=new BufferedReader(new InputStreamReader(System.in));
          }
      }
  
      public boolean hasNext(){
          try{
              String s=br.readLine();
              if(s==null){
                  return  false;
              }
              st=new StringTokenizer(s);
          }catch(IOException e){
              e.printStackTrace();
          }
          return true;
      }
  
      public String next()
      {   
          if(input!=null){
              try {
                  StringBuilder sb=new StringBuilder();
                  int ch=input.read();
                  while(ch=='\n'||ch=='\r'||ch==32){
                      ch=input.read();
                  }
                  while(ch!='\n'&&ch!='\r'&&ch!=32){
                      sb.append((char)ch);
                      ch=input.read();
                  }
                  return sb.toString();
              }catch (Exception e){
                  e.printStackTrace();
              }
          }
          while(st==null || !st.hasMoreElements())//回车，空行情况
          {
              try {
                  st = new StringTokenizer(br.readLine());
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
          return st.nextToken();
      }
  
      public int nextInt()
      {
          return (int)nextLong();
      }
  
      public long nextLong() {
          try {
              if(input!=null){
                  long ret=0;
                  int b=input.read();
                  while(b<'0'||b>'9'){
                      b=input.read();
                  }
                  while(b>='0'&&b<='9'){
                      ret=ret*10+(b-'0');
                      b=input.read();
                  }
                  return ret;
              }
          }catch (Exception e){
              e.printStackTrace();
          }
          return Long.parseLong(next());
      }
  
      public double nextDouble()
      {
          return Double.parseDouble(next());
      }
  }