#include<vector>
#include<algorithm>
#include<fstream>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
const int INF = 2e8;
const int NMAX = 1e5;
int n, m;
vector<int>g[NMAX + 1], gt[NMAX + 1], v, ans;
void dfs1(int node) {
	v[node] = 1;
	for (auto i : g[node])
		if (!v[i]) dfs1(i);
	ans.push_back(node);
}
void dfs2(int node, int k) {
	v[node] = k;
	for (auto i : gt[node])
		if (!v[i]) dfs2(i, k);
}
int main() {
	cin >> n >> m;
	while (m--) {
		int u, v;
		cin >> u >> v;
		g[u].push_back(v);
		gt[v].push_back(u);
	}
	v = vector<int>(n + 1);

	for (int i = 1; i <= n; i++)
		if (!v[i]) dfs1(i);

	int ssc = 0;
	v = vector<int>(n + 1);
	reverse(ans.begin(), ans.end());

	for (auto i : ans)
		if (!v[i]) dfs2(i, ++ssc);

	cout << ssc << '\n';
	for (int i = 1; i <= ssc; i++) {
		for (int j = 1; j <= n; j++)
			if (v[j] == i) cout << j << " ";
		cout << '\n';
	}
	return 0;
}