//记得每次清边
vector<int>Edge[maxm];
stack<int>S;
int Dfn[maxn],Low[maxn],sccno[maxn],tclock,sccnt;//sccno代表某个点所在的强连通分量编号

void tarjan(int u){
    Dfn[u] = Low[u] = ++tclock;
    S.push(u);

    for(int i = 0;i < Edge[u].size();i++){
        int v = Edge[u][i];
        if(!Dfn[v]){
            tarjan(v);
            Low[u] = min(Low[u],Low[v]);
        }
        else if(!sccno[v]){
            Low[u] = min(Low[u],Dfn[v]);
        }
    }

    if(Low[u] == Dfn[u]){
        sccnt ++;
        int v = -1;
        while(v != u){
            v = S.top();
            S.pop();
            sccno[v] = sccnt;
        }
    }
}

void findscc(int n){
    tclock = sccnt = 0;
    //各种数组初始化
    memset(Dfn,0,sizeof(Dfn));
    memset(Low,0,sizeof(Low));
    memset(sccno,0,sizeof(sccno));
    for(int i = 1;i <= n;i++)
        if(!Dfn[i]) tarjan(i);
}