#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin>>t;
while(t--)
{
char res[100000];
string a,b;
cin>>a>>b;
if(a.length()!=b.length())
{
string c=b;
int n=a.length()/b.length();
for(int i=0;i<n-1;i++)
{
b.append(c);
}
}
for(int i=0;i<a.length();i++)
{
int x=a[i]-96+b[i];
if(x>122)
{
x-=122;
x+=96;
}
res[i]=(char)x;
}
cout<<res<<"\n";
}
return 0;
}
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