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: //package codeforces.problemset.score.s_1800.P_1554_C;
  
  import java.io.*;
  import java.util.StringTokenizer;
  
  /**
   * https://codeforces.com/problemset/problem/1554/C
   * C. Mikasa
   * */
  public class Main {
      public static void main(String[] args) throws FileNotFoundException {
          FastScan sc = new FastScan(System.in);
          //FastScan sc = new FastScan("E:\\3.study\\2.git_workspace\\algorithm_topic\\src\\main\\java\\codeforces\\problemset\\score\\s_1600\\P_1539_D\\input_01.txt");
          //FastScan sc = new FastScan("E:\\3.study\\2.git_workspace\\algorithm\\src\\main\\java\\codeforces\\problemset\\segment_tree\\div2_1187_D\\input_01.txt");
          PrintWriter out = new PrintWriter(System.out);
  
          int t = sc.nextInt();
          while(t-- > 0){
              int n = sc.nextInt(), m = sc.nextInt();
              m++;
              int ans = 0;
              for(int i = 30; i >= 0 && n < m; i--){
                  if(((n >> i) & 1) == ((m >> i) & 1)){
                      continue;
                  }
  
                  if(((n >> i) & 1) == 0 && ((m >> i) & 1) == 1){
                      ans |= (1 << i);
                      n |= (1 << i);
                  }
              }
              out.println(ans);
          }
  
          out.flush();
          out.close();
      }
  
      static class FastScan {
          StringTokenizer st;
          BufferedReader br;
  
          public FastScan(InputStream s) {
              br = new BufferedReader(new InputStreamReader(s));
          }
  
          public FastScan(String debugInputFileName) throws FileNotFoundException {
              br = new BufferedReader(new FileReader(debugInputFileName));
          }
  
          public String next() {
              while (st == null || !st.hasMoreTokens()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (Exception e) {
                  }
              }
              return st.nextToken();
          }
  
          public int nextInt() {
              return Integer.parseInt(next());
          }
  
          public long nextLong() {
              return Long.parseLong(next());
          }
      }
  }
  