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 random import randint
  
  
  def mysolve(N, M):
  
      N = bin(N)[2:]
      M = bin(M)[2:]
  
      while len(N) < len(M):
          N = "0"+N
      while len(N) > len(M):
          M = "0"+N
      ans = ["" for _ in range(50)]
      flag = False
      for i in range(len(N)):
          if flag:
              ans[i+1] = "0"
              continue
          if N[i] == M[i]:
              ans[i+1] = "0"
          elif M[i] == "1":
              ans[i+1] = "1"
          else:
              ans[i+1] = "0"
              flag = True
      if not flag:
          i = len(N)-1
          while M[i] == "1" and i >= 0:
              ans[i+1] = "0"
              i = i-1
          ans[i+1] = "1"
          return int("".join(ans), 2)
      else:
          return int("".join(ans), 2)
  
  
  def othersolve(n, m):
      s = set(list(range(10000)))
      for i in range(m+1):
          s.remove(n ^ i)
      print(bin(n))
      print(bin(m))
      print(bin(min(s)))
      return min(s)
  
  
  T = int(input())
  for _ in range(T):
      N, M = list(map(int, input().split()))
      print(mysolve(N, M))
  