#include <iostream>
#include <stack>
#include <vector>
#include <algorithm>
#include <fstream>

using namespace std;

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

const int NMAX = 100005;

int m, n;
vector<int>G[NMAX];
vector<int>Gt[NMAX];
vector<vector<int> >sol;
vector<int>v;
stack<int>st;
bool viz[NMAX];

void read()
{
	fin >> n >> m;
	while (m--)
	{
		int a, b;
		fin >> a >> b;
		G[a].push_back(b);
		Gt[b].push_back(a);
	}
}

void write()
{
	fout << sol.size() << "\n";
	for (vector<int>v : sol)
	{
		for (int it : v)
			fout << it << " ";
		fout << "\n";
	}
}

void dfs(int nod, stack<int>& st)
{
	viz[nod] = true;
	for (vector<int>::iterator it = G[nod].begin(); it != G[nod].end(); it++)
	{
		int nnod = *it;
		if (!viz[nnod])
			dfs(nnod, st);
	}
	st.push(nod);
}

void dfsT(int nod, vector<int> &v)
{
	viz[nod] = true;
	for (vector<int>::iterator it = Gt[nod].begin(); it != Gt[nod].end(); it++)
	{
		int nnod = *it;
		if (!viz[nnod])
			dfsT(nnod, v);
	}
	v.push_back(nod);
}

void solve()
{
	for (int i = 1; i <= n; i++)
		viz[i] = 0;

	for (int nod = 1; nod <= n; nod++)
		if (!viz[nod])
			dfs(nod, st);

	for (int i = 1; i <= n; i++)
		viz[i] = 0;

	while (!st.empty())
	{
		int nod = st.top();
		v.clear();
		st.pop();
		if (!viz[nod]) 
		{
			dfsT(nod, v);
			sort(v.begin(), v.end());
			sol.push_back(v);
		}
	}

}

int main()
{
	read();
	solve();
	write();
	return 0;
}