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.math.*;
  import java.util.*;
  
  public class Main {
  
      static final int MAX_N = 1000010;
      static final int INF = 0x3f3f3f3f;
      static final int mod = 1000000007;
  
  
      public static void main(String[] args) throws IOException {
          initReader(System.in);
  
  
          int T = nextInt();
          for (int i = 1; i <= T; i++)
          solve();
  
  
          pw.flush();
      }
  
  
      /*******************************************************************************************************************************/
  
      public static void solve() throws IOException {
          long n = nextLong();
          long m = nextLong();
  
          long ans = Long.MAX_VALUE;
          for (int i = 30; i >= 0; i--) {
              long re1 = (n >> i) << i;
              long re2 = ((m >> i) + 1) << i;
              ans = Math.min(ans, re1 ^ re2);
          }
  
          pw.println(ans);
      }
  
  
      /*******************************************************************************************************************************/
  
      static class Trie {
          int[][] ch;
          int[] value;
          int size;
  
          Trie (int maxSize) {
              ch = new int[maxSize * 32][2];
              value = new int[maxSize * 32];
              size = 1;
          }
  
          public void insert(int x, int inx) {
              int p = 0;
              for (int i = 30; i >= 0; i--) {
                  int c = x >> i & 1;
                  if (ch[p][c] == 0) ch[p][c] = size++;
                  p = ch[p][c];
              }
              value[p] = inx;
          }
  
          public int query(int x) {
              int p = 0;
              for (int i = 30; i >= 0; i--) {
                 int c = x >> i & 1;
                 if (ch[p][0] == 0) p = ch[p][1];
                 else p = ch[p][0];
              }
              return value[p];
          }
      }
  
      /*******************************************************************************************************************************/
  
      static BufferedReader reader;
      static StringTokenizer tokenizer;
      static PrintWriter pw;
  
      public static void initReader(InputStream input) throws IOException {
          reader = new BufferedReader(new InputStreamReader(input));
          tokenizer = new StringTokenizer("");
          pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
  
  //        reader = new BufferedReader(new FileReader("test.in"));
  //        tokenizer = new StringTokenizer("");
  //        pw = new PrintWriter(new BufferedWriter(new FileWriter("test1.out")));
      }
  
      public static boolean hasNext() {
          try {
              while (!tokenizer.hasMoreTokens()) {
                  tokenizer = new StringTokenizer(reader.readLine());
              }
          } catch (Exception e) {
              return false;
          }
          return true;
      }
  
      public static String next() throws IOException {
          while (!tokenizer.hasMoreTokens()) {
              tokenizer = new StringTokenizer(reader.readLine());
          }
          return tokenizer.nextToken();
      }
  
      public static String nextLine() {
          try {
              return reader.readLine();
          } catch (Exception e) {
              return null;
          }
      }
  
      public static int nextInt() throws IOException {
          return Integer.parseInt(next());
      }
  
      public static long nextLong() throws IOException {
          return Long.parseLong(next());
      }
  
      public static double nextDouble() throws IOException {
          return Double.parseDouble(next());
      }
  
      public static char nextChar() throws IOException {
          return next().charAt(0);
      }
  
      public static short nextShort() throws IOException {
          return Short.parseShort(next());
      }
  
  }
  
  