#include <iostream>
#include <vector>
#include <fstream>
#include <queue>
#include <stack>
using namespace std;

const int nmax = 100005;
vector<int> G[nmax];
vector<int> GI[nmax];

ifstream f("ctc.in");
ofstream g("ctc.out");

int n, m;

int viz[nmax];

int adaugat[nmax];
stack<int>lista;
vector<int> componente[nmax];

int totale;

void read()
{
	f >> n >> m;
	for (int i = 1; i <= m; i++)
	{
		int x, y;
		f >> x >> y;
		G[x].push_back(y);
		GI[y].push_back(x);
	}
}

void dfs(int nod)
{
	viz[nod] = 1;
	for(auto it : G[nod])
	{
		if (!viz[it])
		{
			dfs(it);
		}
	}
	lista.push(nod);
}


void assign(int nod, int root)
{
	adaugat[nod] = 1;
	componente[root].push_back(nod);
	for (auto it : GI[nod])
	{
		if (!adaugat[it])
		{
			assign(it, root);
		}
	}
}

int main()
{
	read();
	for (int i = 1; i <= n; i++)
	{
		if (!viz[i])
		{
			dfs(i);
		}
	}

	while (!lista.empty())
	{
		if (!adaugat[lista.top()])
		{
			assign(lista.top(), totale);
			totale++;
		}
		lista.pop();
	}

	g << totale << '\n';

	for (int i = 0; i <= n-1; i++)
	{
		if (!componente[i].empty())
		{
			for (auto it : componente[i])
			{
				g << it << " ";
			}
			g << '\n';
		}
	}
	return 0;
}