#include <iostream>
#include <vector>
#include <queue>
#include <map>
#include <string>
#include <algorithm>
using namespace std;
vector<string> topologicalSort(map<string, vector<string>>& graph, map<string, int>& inDegree) {
vector<string> result;
priority_queue<string, vector<string>, greater<string>> q; // 最小堆保证字典序
}
int main() {
int n;
while (cin >> n) {
map<string, vector<string>> graph;
map<string, int> inDegree;
