#include<iostream>
#include <vector>
#include<algorithm>
#include<cmath>
using namespace std;
int main()
{
int t;
cin>>t;
while(t!=0)
{
long long int a,b;
cin>>a>>b;
vector <long long int> v,v1;
while (a > 0)
{
v.push_back( a%2 ) ;
a = a / 2;
}
while (b > 0)
{
v1.push_back( b%2 ) ;
b = b / 2;
}
while(v1.size()!=v.size())
{
v.push_back(0);
}
reverse(v.begin(),v.end());
reverse(v1.begin(),v1.end());
for (long long int i = 0; i < v1.size() ; ++i)
{
if ( v[i]+v1[i] == 2)
v1[i]=1;
else if ( v[i]+v1[i] == 1)
v1[i]=1;
else if ( v[i]+v1[i] == 0)
v1[i]=0;
}
long long sum=0;
for (long long int i = (v1.size()-1); i >= 0; i--)
{
sum+=v1[i]*(long long int)pow(2,v1.size()-1-i);
}
cout<<sum<<endl;
t--;
}
return 0;
}