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 os.path
  from math import gcd, floor, ceil
  from collections import *
  import sys
  mod = 1000000007
  INF = float('inf')
  def st(): return list(sys.stdin.readline().strip())
  def li(): return list(map(int, sys.stdin.readline().split()))
  def mp(): return map(int, sys.stdin.readline().split())
  def inp(): return int(sys.stdin.readline())
  def pr(n): return sys.stdout.write(str(n)+"\n")
  def prl(n): return sys.stdout.write(str(n)+" ")
  
  
  if os.path.exists('input.txt'):
      sys.stdin = open('input.txt', 'r')
      sys.stdout = open('output.txt', 'w')
  
  
  def solve():
      n, m = mp()
      ans = 0
      m += 1
      for i in range(30, -1, -1):
          if n >= m:
              break
          if (1 << i) & n == (1 << i) & m:
              continue
          if (1 << i) & m:
              ans |= (1 << i)
              n |= (1 << i)
      pr(ans)
  
  
  for _ in range(inp()):
      solve()
  