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

using namespace std;

const char iname[] = "ctc.in";
const char oname[] = "ctc.out";
const int  nmax    = 100005;

ifstream fin(iname);
ofstream fout(oname);

stack <int> S;
vector<int> Gr[nmax], Gt[nmax], CTC[nmax];
int n, m, i, ans, x, y, j;
int used[nmax];

void DF(int nod)
{	
	used[nod] = 1;
	for(vector<int>::iterator it = Gr[nod].begin(); it != Gr[nod].end(); ++it)
	{
		if(!used[*it])
		{
			used[*it] = 1;
			DF(*it);
		}
	}
	S.push(nod);
}

void DF2(int nod)
{
	used[nod] = 1;
	for(vector<int>::iterator it = Gt[nod].begin(); it != Gt[nod].end(); ++it)
	{
		if(!used[*it])
		{
			used[*it] = 1;
			DF2(*it);
		}
	}
	CTC[ans].push_back(nod);
}
	
int main()
{
	fin >> n >> m;
	for(i = 1; i <= m; i ++)
	{
		fin >> x >> y;
		Gr[x].push_back(y);
		Gt[y].push_back(x);
	}
	
	for(i = 1; i <= n; i ++)
		if(!used[i])
			DF(i);
	
	memset(used, 0, sizeof(used));
	while(!S.empty())
	{
		int nd = S.top();
		if(!used[nd])
		{
			++ans;
			DF2(nd);
		}
		S.pop();
	}
	fout << ans << "\n";
	for(i = 1; i <= ans; i ++)
	{
		for(vector<int>::iterator it = CTC[i].begin(); it != CTC[i].end(); ++it)
			fout << *it << " ";
		fout << "\n";
	}
	return 0;
}