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 sys import stdout
  from sys import stdin
  def get():
      return stdin.readline().strip()
  def getf(sp = " "):
      return [int(i) for i in get().split(sp)]
  def put(a, end = "\n"):
      stdout.write(str(a) + end)
  def putf(a, sep = " ", end = "\n"):
      stdout.write(sep.join([str(i) for i in a]) + end)
       
  #from collections import defaultdict as dd, deque
  #from random import randint, shuffle, sample
  #from functools import cmp_to_key, reduce
  #from math import factorial as fac, acos, asin, atan2, gcd, log, e
  #from bisect import bisect_right as br, bisect_left as bl, insort
  
  def solve(n, m):
      if(n > m):
          return 0
      a = [0] + [int(i) for i in bin(m)[2 :]]
      b = [0] + [int(i) for i in bin(n)[2 :]]
      k = len(a)
      b = [0] * (k - len(b)) + b
      x = 10 ** 12
      for i in range(k):
          if(a[i] == 0):
              a1 = a.copy()
              a1[i] = 1
              for j in range(i + 1, k):
                  a1[j] = b[j]
              num_a = int("".join([str(j) for j in a1]), 2)
              x = min(x, num_a ^ n)
      return x
  
  def main():
      for _ in range(int(get())):
          n, m = getf()
          put(solve(n, m))
  main()
  