#include using namespace std; int n, m; vector> ikeru; vector del; vector tansaku; int u[400000], v[400000]; bool dfs(int i){ tansaku[i] = true; while(!ikeru[i].empty()){ auto jf = ikeru[i].begin(); int j = *jf; if (tansaku[v[j]] || dfs(v[j])){ del[j] = true; ikeru[i].erase(jf); tansaku[i] = false; return true; }else{ ikeru[i].erase(jf); } } tansaku[i] = false; return false; } int main(){ cin >> n >> m; ikeru.resize(n); del.resize(m); tansaku.resize(n); for (int i=0; i> u[i] >> v[i]; u[i]--; v[i]--; ikeru[u[i]].insert(i); } dfs(0); vector> ans; for (int i=0; i