G4 in LOSH 2016

#include <iostream>
#include <vector>
using namespace std;
int o = 100000;
int num1, num2, md[100*100*100], mas[100*100*100], kx;
bool pp;
int sum = 0;
vector<int> all[100000];
bool dfs(int l) {
    md[l]=2;
    //l*=-1;
    //printf("");
    for (int j:all[l]) {
        if (md[j]==0 && j!=l) {
            pp = dfs(j);
            //++sum;
            if (pp==1) {
                //System.print("");
                return 1;
            }
        } else {
            if (md[j]==2 && j!=l) {
                //System.print("");
                return 1;
            }
        }
    }
    mas[kx]=l;
    kx++;
    md[l]=1;
    return 0;
}
int summar(int sum) {
    for (int i=0;i<20;++i) {
        ++sum;
    }
}
int main() {
    cin >> num1 >> num2;
    //summar(sum);
    for (int i=0,a,b; i<num2;++i) {
        cin >> a >> b;
        all[a-1].push_back(b-1);
    }
    //summar(sum);
    for (int i = 0;i<num1;++i) {
        if (md[i]==0) {
            pp = dfs(i);
            if (pp==1) {
                break;
            }
        }
    }
    //summar(sum);
    if (pp==1) {
        cout << -1;
    } else {
        for (int i=num1-1; i>=0;--i) {
            summar(sum);
            cout << mas[i]+1 << "\n";
        }
    }
}