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 collections import Counter, defaultdict, deque
  import bisect
  from sys import stdin, stdout
  from itertools import repeat, permutations
  import math
  import heapq
  
  MOD = 998244353
  def inp(force_list=False):
      re = map(int, raw_input().split())
      if len(re) == 1 and not force_list:
          return re[0]
      return re
  
  def inpf(force_list=False):
      re = map(float, raw_input().split())
      if len(re) == 1 and not force_list:
          return re[0]
      return re
  
  def inst():
      return raw_input().strip()
  
  def gcd(x, y):
     while(y):
         x, y = y, x % y
     return x
  
  def lcm(x, y):
      return x*y/(gcd(x,y))
  
  def qmod(a, b, mod=MOD):
      res = 1
      while b:
          if b&1:
              res = (res*a)%mod
          b >>= 1
          a = (a*a)%mod
          # print b
      return res
  
  def inv(a):
      return qmod(a, MOD-2)
  
  def query(num):
      print num
      stdout.flush()
      return inp()
  
  def my_main():
      kase = inp()
      pans = []
      cur = []
      for _ in range(kase):
          n, m = inp()
          if n>m:
              pans.append('0')
              continue
          n = bin(n)[2:].zfill(33)
          m = bin(m)[2:].zfill(33)
          # print n
          # print m
          ans = []
          ok = 0
          can = -1
          for i in range(33):
              if ok:
                  ans.append('0')
                  continue
              if n[i]== '0' and m[i]== '0':
                  ans.append('0')
                  can = i
                  continue
              if n[i]== '1' and m[i]== '1':
                  ans.append('0')
                  continue
              if n[i]== '1' and m[i]== '0':
                  ok = 1
                  ans.append('0')
                  continue
              if n[i]== '0' and m[i]== '1':
                  ans.append('1')
                  continue
          # print ok
          if ok==0:
              if can != -1:
                  ans[can] = '1'
                  for j in range(can+1, 33):
                      ans[j] = '0'
          # print ''.join(ans)
          # print bin(530866)[2:].zfill(33)
          pans.append(str(int(''.join(ans), 2)))
  
      print '\n'.join(pans)
  
  
  my_main()
  