C

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define _test   int _TEST; cin>>_TEST; while(_TEST--)
#define pb     push_back

int main()
{
    _test
    {
        string x, y;
        cin>>x>>y;

        string a, b;

        int d = -1;

        do{
            d++;
            a.pb(max(x[d], y[d]));
            b.pb(min(x[d], y[d]));
        }while(d+1<x.size() && x[d]==y[d]);

        for(int i=d+1; i<x.size(); i++)
        {
            a.pb(min(x[i], y[i]));
            b.pb(max(x[i], y[i]));
        }

        cout<<a<<"\n"<<b<<"\n";
    }
}