int dfn[maxn] = { 0 }, low[maxn] = { 0 }, idfs = 0;
int sk[maxn] = { 0 }, issk[maxn] = { 0 }, isk = 0;
int scc[maxn] = { 0 }, sz[maxn] = { 0 }, iscc = 0;
int n, m;
vector<int> G[maxn];
vector<int> TG[maxn];

void tarjan(int u) {
    dfn[u] = low[u] = ++ idfs;
    sk[++ isk] = u;
    issk[u] = 1;

    for(auto ne : G[u]) {
        if(!dfn[ne]) {
            tarjan(ne);
            chmin(low[u], low[ne]);
        }else if(issk[ne]) {
            chmin(low[u], low[ne]);
        }
    }

    if(dfn[u] == low[u]) {
        ++ iscc;
        while(sk[isk] != u) {
            scc[sk[isk]] = iscc;
            sz[iscc] ++;
            issk[sk[isk]] = 0;
            isk --;
        }
        scc[sk[isk]] = iscc;
        sz[iscc] ++;
        issk[sk[isk]] = 0;
        isk --;
    }
}

void get_TG() {
    for(int i = 1; i <= n; i ++ ) {
        if(!dfn[i]) {
            tarjan(i);
        }
    }
    set<pii> seg;
    for(int i = 1; i <= n; i ++ ) {
        if(G[i].size()) {
            for(auto ne : G[i]) {
                if(scc[i] != scc[ne]) {
                    seg.insert({scc[i], scc[ne]});
                }
            }
        }
    }
    for(auto p : seg) {
        TG[p.fi].pb(p.se);
    }
}