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.io.*;
  import static java.lang.System.out;
  import java.util.Stack;
  import java.util.Queue;
  
  public class C1554
  {
  
      static int mod=(int)(1e9+7);
      static long MOD=(long)(1e9+7);
      static FastReader in=new FastReader();
      static PrintWriter pr = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
          
      public static void main(String args[])
      {  
  
          int tc=1;
       
          tc=in.nextInt();
          tcloop: while(tc-->0)
          {
              
              int n=in.nextInt();
              int m=in.nextInt();
  
              if(n>m){
                  pr.println(0);
                  continue tcloop;
              }
              
              int num=0;
              int f=0;
              int p=m+1;
              for(int i=30;i>=0;i--)
              {
                  int mask = 1<<i;
                 // pr.println((mask&n)+" "+(mask&p));
                  if((mask&n)!=(mask&p))
                  {
                      if((mask&n)==0)
                      {
                          num+=mask;
                      }
                      else 
                      {
                          break;
                      }
  
                  }
  
              }
              pr.println(num);
  
  
  
  
  
            
  	
  
          }
          pr.flush();
          
      }
  
  	static long gcd(long a,long b)
  	{
  		if(a==0)return b;
  		return gcd(b%a,a);
  	}
  
      
  
      static void sort(long[] a) {
  		ArrayList<Long> l = new ArrayList<>();
  		for (long i : a)
  			l.add(i);
  		Collections.sort(l);
  		for (int i = 0; i < a.length; i++)
  			a[i] = l.get(i);
  	}
      
      
  	static void sort(int[] a) {
  		ArrayList<Integer> l = new ArrayList<>();
  		for (int i : a)
  			l.add(i);
  		Collections.sort(l);
  		for (int i = 0; i < a.length; i++)
  			a[i] = l.get(i);
      }
  
      
      static class FastReader
      { 
          BufferedReader br; 
          StringTokenizer st; 
  
          public FastReader() 
          { 
              br = new BufferedReader(new InputStreamReader(System.in)); 
          } 
  
          String next() 
          { 
              while (st == null || !st.hasMoreElements()) 
              { 
                  try
                  { 
                      st = new StringTokenizer(br.readLine()); 
                  } 
                  catch (IOException  e) 
                  { 
                      e.printStackTrace(); 
                  } 
              } 
              return st.nextToken(); 
          } 
  
          int nextInt() 
          { 
              return Integer.parseInt(next()); 
          } 
  
          long nextLong() 
          { 
              return Long.parseLong(next()); 
          } 
  
          double nextDouble() 
          { 
              return Double.parseDouble(next()); 
          } 
          
          int[] readIntArray(int n)
          {
  		int a[]=new int[n];
  		for(int i=0;i<n;i++)a[i]=nextInt();
  		return a;
  	}
  		
  	long[] readLongArray(int n)
  	{
  		long a[]=new long[n];
  		for(int i=0;i<n;i++)a[i]=nextLong();
  		return a;
  	}
  	
          String nextLine() 
          { 
              String str = ""; 
              try
              { 
                  str = br.readLine(); 
              } 
              catch (IOException e) 
              { 
                  e.printStackTrace(); 
              } 
              return str; 
          } 
      } 
  }
  
  
  
  