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.StringTokenizer;
  
  public class Main {
      
      public static void main(String[] args) throws IOException {
          Scanner scn = new Scanner(System.in);
          OutputWriter out = new OutputWriter(System.out);
          // Always print a trailing "\n" and close the OutputWriter as shown at the end of your output
          
          // example:
          int t=scn.nextInt();
          for(int i=0;i<t;i++){
          int n=scn.nextInt();
          int m=scn.nextInt();
          int[] arr=new int[2];
          arr[0]=m;arr[1]=n;
          int ans=0;
          while(true){
              int a=msb(m);int b=msb(n);
              if(a==b){
                  m-=a;n-=b;
              }
              else if(a>b){
                  ans+=a;m-=a;
              }
              else{
                  break;
              }
              if(a==0&&b==0){
                  ans=med(arr[0]+1,arr[1]);
                  break;
              }
          }
          out.print(ans+"\n");
          }
          out.close();
      }
      public static int msb(int n){
          n |= n >> 1;
          n |= n >> 2;
          n |= n >> 4;
          n |= n >> 8;
          n |= n >> 16;
          n = n + 1;
          return (n >> 1);
      }
      public static int med(int m,int n){
          int ans=0;
          while(true){
              int a=msb(m);int b=msb(n);
              if(a==b){
                  m-=a;n-=b;
              }
              else if(a>b){
                  ans+=a;m-=a;
              }
              else{
                  break;
              }
              if(a==0&&b==0){
                  break;
              }
          }
          return(ans);
      }
  
      // fast input
      static class Scanner {
          public BufferedReader reader;
          public StringTokenizer tokenizer;
  
          public Scanner(InputStream stream) {
              reader = new BufferedReader(new InputStreamReader(stream));
              tokenizer = null;
          }
  
          public String next() {
              while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                  try {
                      String line = reader.readLine();
                      if (line == null)
                          return null;
                      tokenizer = new StringTokenizer(line);
                  } catch (Exception e) {
                      throw(new RuntimeException());
                  }
              }
              return tokenizer.nextToken();
          }
  
          public int nextInt() { return Integer.parseInt(next()); }
          public long nextLong() { return Long.parseLong(next()); }
          public double nextDouble() { return Double.parseDouble(next()); }
      }
  
      // fast output
      static class OutputWriter {
          BufferedWriter writer;
  
          public OutputWriter(OutputStream stream) {
              writer = new BufferedWriter(new OutputStreamWriter(stream));
          }
  
          public void print(int i) throws IOException { writer.write(i); }
          public void print(String s) throws IOException { writer.write(s); }
          public void print(char[] c) throws IOException { writer.write(c); }
          public void close() throws IOException { writer.close(); }
      }
  
  
  }
  
  