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: from os import path
  import sys, time
  # mod = int(1e9 + 7)
  # import re
  from math import ceil, floor, gcd, log, log2, factorial, sqrt
  from collections import defaultdict, Counter, OrderedDict, deque
  from itertools import combinations, accumulate
  # from string import ascii_lowercase ,ascii_uppercase
  from bisect import *
  from functools import reduce
  from operator import mul
  
  star = lambda x: print(' '.join(map(str, x)))
  grid = lambda r: [lint() for i in range(r)]
  INF = float('inf')
  if (path.exists('input.txt')):
      sys.stdin = open('input.txt', 'r')
      sys.stdout = open('output.txt', 'w')
  import sys
  from sys import stdin, stdout
  from collections import *
  from math import gcd, floor, ceil
  
  
  def st():
      return list(stdin.readline().strip())
  
  
  def inp():
      return int(stdin.readline())
  
  
  def inlt():
      return list(map(int, stdin.readline().split()))
  
  
  def invr():
      return map(int, stdin.readline().split())
  
  
  
  
  
  def solve():
      n,m = invr()
      ans = float("inf")
      res = 0
      for i in range(31,-1,-1):
          if (n & pow(2,i)) and not(m & pow(2,i)):
              print(min(ans,res))
              return
          elif (m & pow(2,i)) and not(n & pow(2,i)):
              res += pow(2,i)
          elif not(n & pow(2,i)) and not(m & pow(2,i)):
              ans = min(ans,pow(2,i)+res)
      print(ans)
      return
  
  t = 1
  t = inp()
  for _ in range(t):
      solve()
  