萌新写了个贪心假掉了，求正解及 hack 数据 /kel

int n;
string s[4];

string solve(int x, int y) {
	string ans = "";
	int now = 1;
	rep(i, 1, 2 * n) {
		ans += s[x][i]; 
		if(s[x][i] == s[y][now]) ++now;
	}
	rep(i, now, 2 * n) ans += s[y][i];
	return ans;
}

int main() {
	int T; cin >> T;
	while(T--) {
		int f = 0;
		cin >> n;
		cin >> s[1] >> s[2] >> s[3];
		s[1] = ' ' + s[1], s[2] = ' ' + s[2], s[3] = ' ' + s[3];
		rep(i, 1, 3) {
			rep(j, 1, 3) {
				if(i == j) continue;
				string ans = solve(i, j);
				if(ans.size() <= 3 * n) {
					cout << ans << endl;
					f = 1;
					break;
				}
			}
			if(f) break;
		}
	} 
 	return 0;
}