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.ArrayList;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.PriorityQueue;
  import java.util.StringTokenizer;
  import java.util.TreeSet;
  import java.io.IOException;
  import java.io.BufferedReader;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  
  public class S2 {
  	
  	public static class Reader {
  		
  		static BufferedReader reader;
  		static StringTokenizer tokenizer;
  		
  		static void init(InputStream input) {
  			reader = new BufferedReader(new InputStreamReader(input));
  			tokenizer = new StringTokenizer("");
  		}
  		
  		static String next() throws IOException {
  			while(!tokenizer.hasMoreTokens()) {
  				tokenizer = new StringTokenizer(reader.readLine());
  			}
  			return tokenizer.nextToken();
  		}
  		
  		static int nextInt() throws IOException {
  			return Integer.parseInt(next());
  		}
  		
  		static long nextLong() throws IOException {
  			return Long.parseLong(next());
  		}
  		
  	}
  
  	private static long n;
  	private static long k;
  	private static long x;
  	
  	private static long nl;
  	private static long ans;
  	
  	private final static long fd = 998244353;
  	private final static long mod1 = 1000000007;
  	
  	
  	private final static int sz = 100000;
  	private static long[] arr;
  	private static int[] arri;
  	private static char[] str;
  	
  	public static class Node implements Comparable<Node> {
  		long ai;
  		long bi;
  		public Node(long a, long b) {
  			// TODO Auto-generated constructor stub
  			ai=a;
  			bi=b;
  		}
  		@Override
  		public int compareTo(Node o) {
  			// TODO Auto-generated method stub
  			long dif = bi-o.bi;
  			if(dif>0) {
  				return 1;
  			}
  			else if(dif<0){
  				return -1;
  			}
  			return 0;
  			
  		}
  	}
  	
  	public static void main(String[] args) throws IOException {
  		
  		Reader.init(System.in);
  		
  		PrintWriter out = new PrintWriter(System.out);
  		
  		int tc=1;
  		tc = Reader.nextInt();
  		
  		main_loop:
  			for(int tn=0; tn<tc; tn++) {
  				
  				ans=0;
  				
  				n = Reader.nextInt();
  				long m = Reader.nextInt();
  				ans = solve(n,m);
  								
  				out.print((ans)+"\n");
  			}
  		
  		out.flush();
  		out.close();
  	}
  	
  	private static long solve(long n, long m) {
  		
  		boolean[] nBits = bits(n);
  		boolean[] nCopy = new boolean[32];
  		for(int i=0; i<32; i++) {
  			nCopy[i]=nBits[i];
  		}
  		boolean[] mBits = bits(m);
  		
  		for(int i=31; i>=0; i--) {
  			if(mBits[i]) {
  				nBits[i]=true;
  			}
  			else {
  				if(nBits[i]) {
  					return n^convert(nBits);
  				}
  			}
  		}
  		int i=0;
  		while(nBits[i]) {
  			i++;
  		}
  		nBits[i]=true;
  		i--;
  		while(i>=0) {
  			if(!nCopy[i]) {
  				nBits[i]=false;
  			}
  			i--;
  		}
  		return n^convert(nBits);		
  	}
  	
  	private static long convert(boolean[] bits) {
  		long num=0;
  		for(int i=0; i<32; i++) {
  			if( bits[i]) {
  				num+=1<<i;
  			}
  		}
  		return num;
  	}
  	
  	private static boolean[] bits(long num) {
  		int i=0;
  		boolean[] bArr = new boolean[32];
  		while(num>0) {
  			if((num&1)==1) {
  				bArr[i]=true;
  			}
  			i++;
  			num/=2;
  		}
  		return bArr;
  	}
  
  	private static Long getLast(ArrayList<Long> li) {
  		return li.get(li.size()-1);
  	}
  }