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.io.*;
  import java.util.*;
  
  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()); 
          } 
    
          double nextDouble() 
          { 
              return Double.parseDouble(next()); 
          } 
    
          String nextLine() 
          { 
              String str = ""; 
              try
              { 
                  str = br.readLine(); 
              } 
              catch (IOException e) 
              { 
                  e.printStackTrace(); 
              } 
              return str; 
          } 
      }
      // gives TLE
      public static void solve(int n,int m){
          HashSet<Long> set=new HashSet<>();
          long max=-1;
          for(int i=0;i<=m;i++){
              long x=(n^i);
              set.add(x);
              max=Math.max(max,x);
          }
          for(long i=0;i<=max;i++){
              if(!set.contains(i)){
                  System.out.println(i);
                  return;
              }
          }
          System.out.println(max+1);
      }
      public static int msb(int x){
          int p=0;
          while(x>0){
              x=(x>>>1);
              p++;
          }
          return p-1;
      }
      public static void solve2(int n,int m){
          if(n>m){
              System.out.println(0);
              return;
          }
          int ans=0;
          int x=m+1;
          int place=msb(x);
          for(int p=place;p>=0;p--){
              int mask=(1<<p);
              if( ((x&mask) > 0) && ((n&mask) == 0)){
                  ans|=mask;
              }else if( ((x&mask)==0) && ((n&mask)>0)){
                  break;
              }
          }
          System.out.println(ans);
      }
      public static void main(String[] args) {
          FastReader sc=new FastReader(); 
          
          int t=sc.nextInt();
          while(t-->0){
              int n=sc.nextInt();
              int m=sc.nextInt();
              solve2(n,m);
          }
      }
  }
  // link-> https://codeforces.com/contest/1554/problem/C