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 sys
  from math import *
  import builtins
  import string
  import bisect
  
  alphabets = list(string.ascii_lowercase)
  ALPHABETS = list(string.ascii_uppercase)
  
  # # For getting input from input.txt file
  # sys.stdin = open('input.txt', 'r')
  #
  # # Printing the Output to output.txt file
  # sys.stdout = open('output.txt', 'w')
  
  # input = sys.stdin.readline
  
  
  def print(x, end='\n'):
      sys.stdout.write(str(x) + end)
  
  
  # IO helpers
  def get_int():
      return int(input())
  
  
  def get_list_ints():
      return list(map(int, input().split()))
  
  
  def get_char_list():
      s = input()
      return list(s[:len(s)])
  
  
  def get_tuple_ints():
      return tuple(map(int, input().split()))
  
  
  def print_iterable(p):
      print(" ".join(map(str, p)))
  
  
  def floorSearch(arr, low, high, x):
      if low > high:
          return -1
      if x >= arr[high]:
          return high
      mid = int((low + high) / 2)
      if arr[mid] == x:
          return mid
      if mid > 0 and arr[mid - 1] <= x < arr[mid]:
          return mid - 1
      if x < arr[mid]:
          return floorSearch(arr, low, mid - 1, x)
      return floorSearch(arr, mid + 1, high, x)
  
  
  def binary_search(arr, x):
      low = 0
      high = len(arr) - 1
      mid = 0
      while low <= high:
          mid = (high + low) // 2
          if arr[mid] < x:
              low = mid + 1
          elif arr[mid] > x:
              high = mid - 1
          else:
              return mid
      return high
  
  
  def main():
      p = get_int()
      for q in range(p):
          n, m = get_list_ints()
          ans = 0
          m += 1
          for k in range(30, -1, -1):
              if n >= m:
                  break
              if (n >> k & 1) == (m >> k & 1):
                  pass
              elif (m >> k & 1) == 1:
                  ans |= 1 << k
                  n |= 1 << k
                  m |= 1 << k
          print(ans)
      pass
  
  
  if __name__ == '__main__':
      main()
  