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.CF735;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.PriorityQueue;
  import java.util.StringTokenizer;
  
  public class C {
  
      static final long mod = (long) 1e9 + 7l;
  
      private static void solve(int t) {
          int n = fs.nextInt();
          int m = fs.nextInt();
          ++m;
          int ans = 0;
          for (int k = 30; k >= 0 && n < m; k--) {
              if ((n >> k & 1) == (m >> k & 1)) continue;
              if ((m >> k & 1) != 0) {
                  ans |= 1 << k;
                  n |= 1 << k;
              }
          }
          System.out.println(ans);
      }
  
      public static void main(String[] args) {
          fs = new FastScanner();
          out = new PrintWriter(System.out);
          long s = System.currentTimeMillis();
          int t = fs.nextInt();
          for (int i = 1; i <= t; i++) solve(t);
          out.close();
  //        System.err.println( System.currentTimeMillis() - s + "ms" );
      }
  
      static boolean DEBUG = true;
      static PrintWriter out;
      static FastScanner fs;
  
      static void trace(Object... o) {
          if (!DEBUG) return;
          System.err.println(Arrays.deepToString(o));
      }
  
      static void pl(Object o) {
          out.println(o);
      }
  
      static void p(Object o) {
          out.print(o);
      }
  
      static long gcd(long a, long b) {
          return (b == 0) ? a : gcd(b, a % b);
      }
  
      static int gcd(int a, int b) {
          return (b == 0) ? a : gcd(b, a % b);
      }
  
      static void sieveOfEratosthenes(int n, int factors[]) {
          factors[1] = 1;
          for (int p = 2; p * p <= n; p++) {
              if (factors[p] == 0) {
                  factors[p] = p;
                  for (int i = p * p; i <= n; i += p)
                      factors[i] = p;
              }
          }
      }
  
      static long mul(long a, long b) {
          return a * b % mod;
      }
  
      static long fact(int x) {
          long ans = 1;
          for (int i = 2; i <= x; i++) ans = mul(ans, i);
          return ans;
      }
  
      static long fastPow(long base, long exp) {
          if (exp == 0) return 1;
          long half = fastPow(base, exp / 2);
          if (exp % 2 == 0) return mul(half, half);
          return mul(half, mul(half, base));
      }
  
      static long modInv(long x) {
          return fastPow(x, mod - 2);
      }
  
      static long nCk(int n, int k) {
          return mul(fact(n), mul(modInv(fact(k)), modInv(fact(n - k))));
      }
  
      static class FastScanner {
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer st = new StringTokenizer("");
  
          public String next() {
              while (!st.hasMoreElements())
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              return st.nextToken();
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          int[] readArray(int n) {
              int[] a = new int[n];
              for (int i = 0; i < n; i++)
                  a[i] = nextInt();
              return a;
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
      }
  }
  