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.*;
  
  public class C {
  	public static void main(String[] args) throws IOException {
  		Kattio io = new Kattio();
  
  		int t = io.nextInt();
  
  		for (int ii=0; ii<t; ii++) {
  			long n = io.nextInt();
  			long m = io.nextInt();
  
  			long ans = Long.MAX_VALUE;
  			
  			for (int i=31; i>=0; i--) {
  				long aa = (n>>i)<<i; 
  				long bb = ((m>>i)+1)<<i;
  				ans = Math.min(ans, aa^bb);
  			}
  
  			io.println(ans);
  		}
  		io.close();
  	}
  
  	static class Kattio extends PrintWriter {
  		private BufferedReader r;
  		private StringTokenizer st;
  
  		// standard input
  		public Kattio() { this(System.in, System.out); }
  		public Kattio(InputStream i, OutputStream o) {
  			super(o);
  			r = new BufferedReader(new InputStreamReader(i));
  		}
  		// USACO-style file input
  		public Kattio(String problemName) throws IOException {
  			super(new FileWriter(problemName + ".out"));
  			r = new BufferedReader(new FileReader(problemName + ".in"));
  		}
  
  		// returns null if no more input
  		public String next() {
  			try {
  				while (st == null || !st.hasMoreTokens())
  					st = new StringTokenizer(r.readLine());
  				return st.nextToken();
  			} catch (Exception e) { }
  			return null;
  		}
  
  		public int nextInt() { return Integer.parseInt(next()); }
  		public double nextDouble() { return Double.parseDouble(next()); }
  		public long nextLong() { return Long.parseLong(next()); }
  	}
  }