for (int i = 1; i <= n; i++) {
		scanf("%lld", &d[i]);
		cnt += d[i];
	    for (int j = 1; j <= d[i]; j++) {
	    	ll v;
	    	scanf("%lld", &v);
	    	in[v]++;
	    	b[v]++;
	    	add_edge(i, v);
	    }
	}
	assert(cnt < 2 * N);

在luogu不会RE