int n, e;
std::vector<int> adj[200000];
std::vector<int> color; // 0 - not visited,1 = entered for visit,2 = visited
std::vector<int> parent;
int cycle_start, cycle_end;

bool dfs(int v){
    color[v] = 1;
    for(auto u : adj[v]){
        if(color[u] == 0){
            parent[u] = v;
            if(dfs(u))return true;
        }
        else if(color[u] == 1){
            cycle_end = v;
            cycle_start = u;
            return true;
        }
    }
    color[v] = 2;
    return false;
}