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.util.*;
  import java.util.Map.Entry;
  import java.lang.*;
  import java.io.*;
  import java.math.BigInteger;
  
  
  public class CF {
  	private static FS sc = new FS();
  	
  	private static class FS {
  		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  		StringTokenizer st = new StringTokenizer("");
  		String next() {
  			while (!st.hasMoreTokens())
  				try {
  					st=new StringTokenizer(br.readLine());				               
  	            } catch (IOException e) {}
  			return st.nextToken();
  		}
  		
  		int nextInt() {
  			return Integer.parseInt(next());
  		}
  		long nextLong() {
  			return Long.parseLong(next());
  		}
  	}
  	
  	private static class extra {
  		
  		static int[] intArr(int size) {
  			int[] a = new int[size];
  			for(int i = 0; i < size; i++) a[i] = sc.nextInt();
  			return a;
  		}
  		
  		static long[] longArr(int size) {
  			long[] a = new long[size];
  			for(int i = 0; i < size; i++) a[i] = sc.nextLong();
  			return a;
  		}
  		
  		static long intSum(int[] a) {
  			long sum = 0; 
  			for(int i = 0; i < a.length; i++) {
  				sum += a[i];
  			}
  			return sum;
  		}
  		
  		static long longSum(long[] a) {
  			long sum = 0; 
  			for(int i = 0; i < a.length; i++) {
  				sum += a[i];
  			}
  			return sum;
  		}
  		
  		static LinkedList[] graphD(int vertices, int edges) {
  			LinkedList<Integer>[] temp = new LinkedList[vertices+1];
  			for(int i = 0; i <= vertices; i++) temp[i] = new LinkedList<>();
  			for(int i = 0; i < edges; i++) {
  				int x = sc.nextInt();
  				int y = sc.nextInt();
  				temp[x].add(y);
  			}
  			return temp;
  		}
  		
  		static LinkedList[] graphUD(int vertices, int edges) {
  			LinkedList<Integer>[] temp = new LinkedList[vertices+1];
  			for(int i = 0; i <= vertices; i++) temp[i] = new LinkedList<>();
  			for(int i = 0; i < edges; i++) {
  				int x = sc.nextInt();
  				int y = sc.nextInt();
  				temp[x].add(y);
  				temp[y].add(x);
  			}
  			return temp;
  		}
  		
  		static void printG(LinkedList[] temp) {
  			for(LinkedList<Integer> aa:temp) System.out.println(aa);
  		}
  		
  		static long cal(long val, long pow) {
  			if(pow == 0) return 1;
  			long res = cal(val, pow/2);
  			
  			long ret = (res*res)%mod;
  			if(pow%2 == 0) return ret;
  			return (val*ret)%mod;
  		}
  		
  		static long gcd(long a, long b) { return b == 0 ? a:gcd(b, a%b); }
  		
  	}
  	
  	static int mod = 998244353;//(int) 1e9 + 7;
  //	static int mod = (int) 998244353;
  	static int max = (int) 1e6, sq = 316;
  	static LinkedList<Integer>[] temp;
  //	static int[] par, rank;
  
  	static class pair {
  		int val, idx;
  		pair(int x, int y) { val = x; idx = y; }
  	}
  	
  	public static void main(String[] args) {	
  		int t = sc.nextInt();
  //		int t = 1;
  		StringBuilder ret = new StringBuilder();
  		while(t-- > 0) {
  			int n = sc.nextInt();
  			int m = sc.nextInt();
  			int ans = 0;
  			int req = m+1;
  			for(int i = 31; i >= 0; i--) {
  				int val = 1 << i;
  				int v1 = n&val;
  				int v2 = req&val;
  				if(v1 == v2) continue;
  				else if(v1 != 0 && v2 == 0) {
  					break;
  				} else {
  					ans ^= val;
  				}
  			}
  			ret.append(ans + "\n");
     		}
  		System.out.println(ret);
  	}
  	
  }