#include <bits/stdc++.h>

using namespace std;

#define NMAX 100005

vector<int> suc[NMAX + 1], pred[NMAX + 1];
vector<int> ctc[NMAX + 1];
vector<int> s;
int viz[NMAX];
int nc;

void dfs(int x)
{
	viz[x] = 1;
	for (auto y : suc[x]) {
		if (!viz[y])
			dfs(y);
	}
	s.push_back(x);
}

void dfs_t(int x)
{
	ctc[nc].push_back(x);
	viz[x] = 1;
	for (auto y : pred[x]) {
		if (!viz[y])
			dfs_t(y);
	}
}

int main()
{
	ifstream fin("ctc.in");
	ofstream fout("ctc.out");
	int n, m, x, y;
	fin >> n >> m;
	for (int i = 0; i < m; i++) {
		fin >> x >> y;
		suc[x].push_back(y);
		pred[y].push_back(x);
	}
	for (int i = 1; i <= n; i++) {
		if (!viz[i])
			dfs(i);
	}
	for (int i = 0; i <= n; i++)
		viz[i] = 0;

	for (int i = (int)s.size() - 1; i >= 0; i--) {
		if (!viz[s[i]]) {
			nc++;
			dfs_t(s[i]);
		}
	}

	fout << nc << "\n";
	for (int i = 1; i <= nc; i++) {
		//sort(ctc[i].begin(), ctc[i].end());
		for (auto x : ctc[i]) {
			fout << x << " ";
		}
		fout << "\n";
	}
	return 0;
}