#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;
int N; // numarul de noduri 1...N
vector<vector<int> > G;  // graful propriu-zis
vector<vector<int> > GT; // graful transpus
vector<int> st; // stack sa punem nodurile la primu dfs
vector<int> viz; // vizitat
vector<int> lst; // ultima_componenta

// dfs-ul pe grafu normal.. ca sa vedem de unde tre sa incepem
inline void dfs(int nod) {
	viz[nod] = 1;
	for (int i = 0; i < G[nod].size(); ++i) {
		int nod2 = G[nod][i];
		if (!viz[nod2]) dfs(nod2);
	}
	st.push_back(nod);
}
// dfs-ul pe T
inline void dfs_t(int nod) {
	viz[nod] = 1;
	lst.push_back(nod);
	for (int i = 0; i < GT[nod].size(); ++i) {
		int nod2 = GT[nod][i];
		if (!viz[nod2]) dfs_t(nod2);
	}
}
// afla componentele tari conexe
vector<vector<int> > ctc() {
	vector<vector<int> > ret;
	viz.assign(N+1, 0);
	for (int i = 1; i <= N; ++i)
		if (!viz[i]) dfs(i);

	viz.assign(N+1, 0);
	for (int i = st.size() - 1; i >= 0; --i) 
		if (!viz[st[i]]) {
			lst.resize(0);
			dfs_t(st[i]);
			ret.push_back(lst);
		}
	return ret;
}
int main() {
	freopen("ctc.in", "r", stdin);
	freopen("ctc.out", "w", stdout);
	int M;
	scanf("%d %d", &N, &M);
	G.resize(N+1); GT.resize(N+1);
	while (M--) {
		int a, b;
		scanf("%d %d", &a, &b);
		G[a].push_back(b);
		GT[b].push_back(a);
	}
	vector<vector<int> > com = ctc();
	printf("%d\n", com.size());
	for (int i = 0 ; i < com.size(); ++i) {
		for (int j = 0; j < com[i].size(); ++j) printf("%d ", com[i][j]);
		printf("\n");
	}
	return 0;
}