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: 
  def naiveSolve(n,m):
      
      v=set()
      for i in range(m+1):
          v.add(n^i)
      for i in range(int(1e9)):
          if i not in v:
              return i
      
      return
  
  twoPowers=set()
  x=1
  while x<1e9:
      twoPowers.add(x)
      x*=2
  def solve(n,m):
      # a^b^b=a
      # let x be the mex
      # let n^y=x, y>m, x is smallest possible
      # n^n^y=n^x
      # y=n^x
      # Find smallest possible x such that n^x>m
      
      if n>m:
          return 0
      if m+1 in twoPowers: # m's binary is ..1111
          return m+1
      ans=0
      for i in range(29,-1,-1):
          if (m&(1<<i))>0 and (n&(1<<i))==0:
              ans+=(1<<i) # this bit must be set so that n^ans >= m
              if n^ans>m:
                  return ans
      # if ans hasn't been returned, it is == m.
      assert n^ans==m
      # find smallest 0 bit in m and set it to 1 in ans, and set all smaller bits to 0
      for i in range(31):
          if (m&(1<<i))==0:
              ans=(ans|(1<<i)) # set to 1 and return
              return ans
          ans=(ans&(~(1<<i)))
      
      pass
  
  # for n in range(10):
  #     arr=[]
  #     for m in range(10):
  #         arr.append('m:{} ans:{}'.format(m,naiveSolve(n,m)))
  #     print('n:{}'.format(n))
  #     print(' - '.join(arr))
  
  # print(naiveSolve(1,9))
  # for n in range(200):
  #     for m in range(200):
  #         assert solve(n,m)==naiveSolve(n,m)
  
  def main():
      
      t=int(input())
      allans=[]
      for _ in range(t):
          n,m=readIntArr()
          allans.append(solve(n,m))
          
      multiLineArrayPrint(allans)
      
      return
  
  
  
  import sys
  input=sys.stdin.buffer.readline #FOR READING PURE INTEGER INPUTS (space separation ok)
  # input=lambda: sys.stdin.readline().rstrip("\r\n") #FOR READING STRING/TEXT INPUTS.
  
  def oneLineArrayPrint(arr):
      print(' '.join([str(x) for x in arr]))
  def multiLineArrayPrint(arr):
      print('\n'.join([str(x) for x in arr]))
  def multiLineArrayOfArraysPrint(arr):
      print('\n'.join([' '.join([str(x) for x in y]) for y in arr]))
   
  def readIntArr():
      return [int(x) for x in input().split()]
  # def readFloatArr():
  #     return [float(x) for x in input().split()]
   
  def makeArr(defaultValFactory,dimensionArr): # eg. makeArr(lambda:0,[n,m])
      dv=defaultValFactory;da=dimensionArr
      if len(da)==1:return [dv() for _ in range(da[0])]
      else:return [makeArr(dv,da[1:]) for _ in range(da[0])]
   
  def queryInteractive(x):
      print('{}'.format(x))
      sys.stdout.flush()
      return int(input())
   
  def answerInteractive(ans):
      print('! {}'.format(ans))
      sys.stdout.flush()
   
  inf=float('inf')
  # MOD=10**9+7
  MOD=998244353
  
  from math import gcd,floor,ceil
  # from math import floor,ceil # for Python2
   
  for _abc in range(1):
      main()