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.*;
  import java.math.*;
  
  public class Main
  {
      static class FastReader 
      { 
          BufferedReader br; 
          StringTokenizer st; 
    
          public FastReader() 
          { 
              br = new BufferedReader(new
                       InputStreamReader(System.in)); 
          } 
    
          String n() 
          { 
              while (st == null || !st.hasMoreElements()) 
              { 
                  try
                  { 
                      st = new StringTokenizer(br.readLine()); 
                  } 
                  catch (IOException  e) 
                  { 
                      e.printStackTrace(); 
                  } 
              } 
              return st.nextToken(); 
          } 
    
          int ni() 
          { 
              return Integer.parseInt(n()); 
          } 
    
          long nl() 
          { 
              return Long.parseLong(n()); 
          } 
    
          double nd() 
          { 
              return Double.parseDouble(n()); 
          } 
    
          String nline() 
          { 
              String str = ""; 
              try
              { 
                  str = br.readLine(); 
              } 
              catch (IOException e) 
              { 
                  e.printStackTrace(); 
              } 
              return str; 
          } 
      }
  
     
       public static long[] randomize(long arr[])
      {
          Random rand = new Random();
  for (int i = 0; i < arr.length; ++i) {
     int index = rand.nextInt(arr.length - i);
     long tmp = arr[arr.length - 1 - i];
     arr[arr.length - 1 - i] = arr[index];
     arr[index] = tmp;
  }
  
  return arr;
      } 
  
      static long mod = 1000000007;
  
    
      public static void main (String[] args) throws java.lang.Exception
      {
          FastReader sc = new FastReader();
          StringBuilder fo = new StringBuilder();
  
          int test=sc.ni();
          
          while(test-->0)
          {
  
              long n = sc.ni();
              long m = sc.nl()+1;
              long ans =0;
              long l =0, u = n^m;
              while(l<=u)
              {
                  long mid = l+(u-l)/2;
                  long curr = n^mid;
                 // System.out.println(l+" "+u);
                  if(curr>= m)
                  {
                      u = mid-1;
                      ans = mid;
                  }
                  else
                      l = mid + 1;
              }
  
              System.out.println(ans);
           
          }
          
          
          
      }
      
      
      
      
  }
  