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.lang.*;
  import java.io.*;
  public class Main{
      static class FastReader{
          BufferedReader br;
          StringTokenizer st;
          public FastReader(){
              br = new BufferedReader(new InputStreamReader(System.in));
          }
          String next(){
              while(st == null || !st.hasMoreElements()){
                  try{
                      st = new StringTokenizer(br.readLine());
                  }
                  catch(IOException e){
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
          int nextInt(){
              return Integer.parseInt(next());
          }
          long nextLong(){
              return Long.parseLong(next());
          }
          String nextLine(){
              String sr = "";
              try{
                  sr = br.readLine();
              }
              catch(IOException e){
                  e.printStackTrace();
              }
              return sr;
          }
      }
      public static void main(String args[]) throws Exception{
          FastReader ft = new FastReader();
          BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));
          int t = ft.nextInt();
          while(t-->0){
              int a = ft.nextInt();
              int b = ft.nextInt();
              if(a>b)
              out.write("0 \n");
              else{
                int ans = 0;
                int bit = 31;
                for(int i =30;i>=0;i--){
                   if((((1<<i)&a)!=0)&&(((1<<i)&(b+1))==0))
                   { 
                   break;}
                   else if((((1<<i)&a)==0)&&(((1<<i)&(b+1))!=0))
                   ans |= (1<<i);
                   
                   
                }
                out.write(ans+"\n");
              }
              }
          out.flush();
              }
     
  }