KOI: Sandro

#include <bits/stdc++.h>
using namespace std;

const int N = 2e4 + 5;

vector<int> adj[N];
int inDeg[N];

int main(){

    int nVertex, nEdge;
    scanf("%d%d", &nVertex, &nEdge);
    for(int i = 1; i <= nEdge; ++i){
        int u, v;
        scanf("%d%d", &u, &v);
        adj[u].push_back(v);
        ++inDeg[v];
    }
    priority_queue<int, vector<int>, greater<int>> pq;
    for(int i = 1; i <= nVertex; ++i){
        if(inDeg[i] == 0){
            pq.push(i);
        }
    }
    vector<int> topo;
    while(!pq.empty()){
        int u = pq.top();
        pq.pop();
        topo.push_back(u);
        for(int v : adj[u]){
            --inDeg[v];
            if(inDeg[v] == 0){
                pq.push(v);
            }
        }
    }
    if(topo.size() < nVertex){
        cout << "-1";
    } else {
        for(int x : topo){
            cout << x << ' ';
        }
    }

    return 0;
}