#include <cstdio>
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <set>
using namespace std;

set<string> res;
string s1, s2;

void go(int p1, int p2, string cur) {
    if(p1 == s1.size() && p2 == s2.size()) {
        res.insert(cur);
        return;
    }
    if(p1 < s1.size()) {
        go(p1 + 1, p2, cur + s1[p1]);
    }
    if(p2 < s2.size()) {
        go(p1, p2 + 1, cur + s2[p2]);
    }
}
int main()
{
    //freopen("input.txt","rt",stdin);
    //freopen("output.txt","wt",stdout);
    //freopen("console.in","rt",stdin);
    //freopen("console.out","wt",stdout);

    int T;
    scanf("%d", &T);
    while(T--) {
        cin >> s1 >> s2;
        res.clear();
        go(0, 0, "");
        for(set<string>::iterator it = res.begin(); it != res.end(); it++)
                cout << *it << endl;
        cout << endl;
    }

    return 0;
}