main.cxx

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

set<string> res;

void go(int p1, string s1, int p2, string s2, string cur) {
	if(p1 == s1.size() && p2 == s2.size()) {
		res.insert(cur);
		return;
	}
	if(p1 < s1.size()) {
		go(p1 + 1, s1, p2, s2, cur + s1[p1]);
	}
	if(p2 < s2.size()) {
		go(p1, s1, p2 + 1, s2, cur + s2[p2]);
	}
}
int main()
{

	int T;
	scanf("%d", &T);
	
	while(T--) {
		res.clear();
		
		char b1[100], b2[100];
		scanf("%s %s", b1, b2);
		
		go(0, string(b1), 0, string(b2), "");
		
		for(set<string>::iterator it = res.begin(); it != res.end(); it++)
				cout << *it << endl;
		cout << endl;
	}

	return 0;
}