#include <fstream>
#include <vector>

const int nmax = 1e5 + 5;

std::vector<int>in[nmax], out[nmax], ans[nmax], st;
int viz[nmax], k;

void dfs(int node, int type) {
	viz[node] = type;
	if (type == 1) {
		for (auto x : in[node]) if (viz[x] == 0) dfs(x, type);
		st.push_back(node);
	}
	else {
		ans[k].push_back(node);
		for (auto x : out[node]) if (viz[x] == 1) dfs(x, type);
	}
}

int main() {
	std::ifstream fin("ctc.in");
	std::ofstream fout("ctc.out");
	int n, m, u, v;
	fin >> n >> m;
	for (int i = 0; i < m; i++) {
		fin >> u >> v;
		in[u].push_back(v);
		out[v].push_back(u);
	}
	for (int i = 1; i <= n; i++)
		if (!viz[i]) dfs(i, 1);
	while (st.size()) {
		int node = st.back();
		st.pop_back();
		if (viz[node] == 1) k++, dfs(node, 2);
	}
	fout << k;
	for (int i = 1; i <= k; i++) {
		fout << "\n";
		for (auto x : ans[i])
			fout << x << " ";
	}
}