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.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.util.StringTokenizer;
  
  public class pre55 {
      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;
          }
      }
      static int integerfrmbinary(String str){
          double j=0;
          for(int i=0;i<str.length();i++){
              if(str.charAt(i)== '1'){
                  j=j+ Math.pow(2,str.length()-1-i);
              }
  
          }
          return (int) j;
      }
      public static void main(String args[]){
          FastReader obj = new FastReader();
          int tc = obj.nextInt();
          while(tc--!=0){
              int n = obj.nextInt(),m = obj.nextInt();
             // System.out.println(Integer.toBinaryString((int)Math.pow(2,30)));
              if(n>m) System.out.println(0);
              else{
                  m+=1;
                  String ans = "";
                  String ns = Integer.toBinaryString(n),ms = Integer.toBinaryString(m);
                 // System.out.println(ns+" "+ms);
                  while(ns.length()>ms.length()) ms = "0"+ms;
                  while(ms.length()>ns.length()) ns = "0"+ns;
                //  System.out.println(ns+" "+ms);
                  for(int i=0;i<ms.length();i++){
                      if(ms.charAt(i)=='0' && ns.charAt(i)=='0') ans = "0"+ans;
                      else if(ns.charAt(i)=='1' && ms.charAt(i)=='1') ans ="0"+ans;
                      else if(ns.charAt(i)=='0' && ms.charAt(i)=='1') ans = "1" +ans;
                      else if(ns.charAt(i)=='1' && ms.charAt(i)=='0') {
                          ans = "0"+ans;
                          break;
                      }
                  }
                  while(ms.length()>ans.length()) ans="0"+ans;
                  System.out.println(integerfrmbinary((new StringBuilder(ans)).reverse().toString()));
              }
          }
      }
  }
  