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.Arrays;
  import java.util.Random;
  import java.util.StringTokenizer;
  
  public final class C {
  
      public static void main(String[] args) {
          final FastScanner fs = new FastScanner();
          final StringBuilder sb = new StringBuilder();
          final int t = fs.nextInt();
          for (int test = 0; test < t; test++) {
              final int n = fs.nextInt();
              final int m = fs.nextInt() + 1;
              int res = 0;
              for (int i = 30; i >= 0; i--) {
                  if ((n & (1 << i)) == 0 && (m & (1 << i)) != 0) {
                      res |= 1 << i;
                  } else if ((n & (1 << i)) != 0 && (m & (1 << i)) == 0) {
                      break;
                  }
              }
              sb.append(res).append('\n');
          }
          System.out.println(sb);
      }
  
      static final class Utils {
          private static class Shuffler {
              private static void shuffle(int[] x) {
                  final Random r = new Random();
  
                  for (int i = 0; i <= x.length - 2; i++) {
                      final int j = i + r.nextInt(x.length - i);
                      swap(x, i, j);
                  }
              }
  
              private static void shuffle(long[] x) {
                  final Random r = new Random();
  
                  for (int i = 0; i <= x.length - 2; i++) {
                      final int j = i + r.nextInt(x.length - i);
                      swap(x, i, j);
                  }
              }
  
              private static void swap(int[] x, int i, int j) {
                  final int t = x[i];
                  x[i] = x[j];
                  x[j] = t;
              }
  
              private static void swap(long[] x, int i, int j) {
                  final long t = x[i];
                  x[i] = x[j];
                  x[j] = t;
              }
          }
  
          public static void shuffleSort(int[] arr) {
              Shuffler.shuffle(arr);
              Arrays.sort(arr);
          }
  
          public static void shuffleSort(long[] arr) {
              Shuffler.shuffle(arr);
              Arrays.sort(arr);
          }
  
          private Utils() {}
      }
  
      static class FastScanner {
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer st = new StringTokenizer("");
  
          private String next() {
              while (!st.hasMoreTokens()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      //noinspection CallToPrintStackTrace
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
  
          int[] nextIntArray(int n) {
              final int[] a = new int[n];
              for (int i = 0; i < n; i++) { a[i] = nextInt(); }
              return a;
          }
  
          long[] nextLongArray(int n) {
              final long[] a = new long[n];
              for (int i = 0; i < n; i++) { a[i] = nextLong(); }
              return a;
          }
      }
  }
  