#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

const int N = 1e5 + 5;

vector<int> g[N], gt[N], ordine, componenteConexe[N];
bool vizitat[N], cc[N];

void dfs1(int nod)
{
	vizitat[nod] = true;

	for (int next : g[nod])
		if (!vizitat[next])
			dfs1(next);

	ordine.push_back(nod);
}

void dfs2(int nod, int ccx)
{
	cc[nod] = true;
	componenteConexe[ccx].push_back(nod);

	for (int next : gt[nod])
		if (!cc[next])
			dfs2(next, ccx);
}

int main()
{
	int n, m;
	fin >> n >> m;

	for (int i = 0; i < m; i++)
	{
		int x, y;
		fin >> x >> y;
		g[x].push_back(y);
		gt[y].push_back(x);
	}

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

	int cci = 1;
	for (int i = ordine.size() - 1; i >= 0; i--)
	{
		if (!cc[ordine[i]])
			dfs2(ordine[i], cci++);
	}

	fout << cci - 1 << '\n';
	for (int i = 1; i < cci; i++)
	{
		for (int nod : componenteConexe[i])
			fout << nod << ' ';
		fout << '\n';
	}
}