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struct tarjan {
int cnt, scc_num, scc[MN], in[MN], low[MN];
stack<int> s;
bitset<MN> ins;
void tarjan(vector<int> * G, int u) {
low[u] = in[u] = cnt++, ins[u] = 1; s.push(u);
for (int v : G[u]) {
if (in[v] == -1) tarjan(G, v), low[u] = min(low[u], low[v]);
else if (ins[v]) low[u] = min(low[u], in[v]);
}
if (low[u] == in[u]) {
while (1) {
int x = s.top(); s.pop();
scc[x] = scc_num, ins[x] = 0;
if (x == u) break;
}
++scc_num;
}
}
void find_scc(vector<int> * G) {
memset(scc, -1, sizeof scc), memset(in, -1, sizeof in);
for (int u = 1; u <= N; ++u) if (scc[u] == -1) tarjan(G, u);
}
}
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