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.BufferedReader;
  import java.io.BufferedWriter;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.PriorityQueue;
  import java.util.Queue;
  import java.util.StringTokenizer;
  import java.util.TreeMap;
  import java.util.Map.Entry;
  
  
  public class main {
  	private static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  	private static BufferedWriter w=new BufferedWriter(new OutputStreamWriter(System.out));
  	
  	public static void main(String[] args) throws IOException {
  		// TODO Auto-generated method stub
  		int t=Integer.parseInt(br.readLine());
  
  		while(t>0) {
  		    StringTokenizer st = new StringTokenizer(br.readLine());
  		    long n=Long.parseLong(st.nextToken());
  		    long m=Long.parseLong(st.nextToken());
  		    if(m<n) {
  		    	w.write(0+"\n");
  		    }
  		    else {
  		    	String res=calc(n, m+1);
  		    	long ans=Long.parseLong(res, 2);
  		    	w.write(ans+"\n");
  		    }
  			t--;
  		}
  		w.flush();
  		w.close();
  	}
      public static String calc(long n,long m) {
      	String s1=Long.toBinaryString(n);
      	String s2=Long.toBinaryString(m);
      	//make lengths equal;
      	while(s1.length()<s2.length()) {
      		s1=0+s1;
      	}
      //	System.out.println(s1+" "+s2);
      	int i=0;
      	String res="";
      	while(i<s1.length()) {
      		int b1=Integer.parseInt(s1.charAt(i)+"");
      		int b2=Integer.parseInt(s2.charAt(i)+"");
      		if(b1==b2) {
      			res+=0;
      		}
      		else if(b1==0 && b2==1) {
      			res+=1;
      		}
      		else {
      			//found mex
      			int zeroes=s1.length()-res.length();
      			res+=("0").repeat(zeroes);
      			break;
      		}
      		i++;
      	}
      	return res;
      }
  }