TopSortMinLex

#include <bits/stdc++.h>

using namespace std;

#define MAXN 100005

typedef vector < int > Vec;
int N, M, deg[MAXN], nr;
Vec G[MAXN];
priority_queue < int > Q;

inline void read () {
    int a, b;
    cin >> N >> M;
    while (M  --) {
        cin >> a >> b;
        G[a].emplace_back (b);
        deg[b] ++;
    }
    for (int i = 1; i <= N; ++i) if (deg[i] == 0) Q.push (-i);
}

inline void solve () {
    Vec::iterator it;
    while (Q.size()) {
        nr = -Q.top();
        Q.pop();
        cout << nr << " ";
        for (it = G[nr].begin(); it != G[nr].end(); ++it) {
            deg[*it] --;
            if (deg[*it] == 0) Q.push (-*it);
        }
    }
}

int main () {
    read();
    solve();
    return 0;
}