func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     list<int> L;     int N, M;     cin >> N >> M;     set<pair<int, int> > S;     for (int i = 0; i < M; ++i) {       int u, v;       cin >> u >> v;       S.insert(pair<int, int>(u, v));     }     L.push_back(1);     for (int i = 2; i <= N; ++i) {       list<int>::iterator it = L.begin();       while (it != L.end() && S.count(pair<int, int>(i, *it))) it++;       L.insert(it, i);     }     for (list<int>::iterator it = L.begin(); it != L.end(); ++it) {       cout << *it <<    ;     }     cout << endl;   }   