bool used[MAXN];
int tin[MAXN],fup[MAXN],timer;
stack<pii> st;
vector<vector<pii> > com;
void dfs(int v,int p){
    used[v] = 1;
    fup[v] = timer;
    tin[v] = timer++;
    int child = 0;
    for(int to:g[v]){
        if(to==p)
            continue;
        if(used[to]){
            if(tin[to] < fup[v]){
                fup[v] = tin[to];
                st.push({v,to});
            }

        } else{
            child++;
            st.push({v,to});
            dfs(to,v);
            fup[v] = min(fup[v],fup[to]);
            if(p==-1 && child>1){
          //      cout << "ver " << v <<" "<<to<<endl;
                vector<pii> temp;
                while(st.top()!=make_pair(v,to)){
                    temp.pb(st.top());
                    st.pop();
                }
                temp.pb(st.top());
                st.pop();

                com.pb(temp);
            }
            if(p!=-1 && fup[to]>=tin[v]){
         //       cout << "ver " << v <<" "<<to<<endl;
               vector<pii> temp;
                while(st.top()!=make_pair(v,to)){
                    temp.pb(st.top());
                    st.pop();
                }
                temp.pb(st.top());
                st.pop();

                com.pb(temp);
            }

        }
    }
}