Ultra fast mathematics

my logic seems correct but i havn’t got required output.
#include<bits/stdc++.h>
using namespace std;
main()
{
int t;
cin>>t;
while(t–)
{
string n1,n2,ans;
cin>>ws;
cin>>n1>>n2;
int i;
for(i=0;i<n1.length();i++)
{
char temp=n1[i]^n2[i];
ans.push_back(temp);
}
cout<<ans<<"\n";
}
}