#include <iostream>
#include <fstream>
#include <vector>
#define NMAX 100000

using namespace std;

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

int n, m, viz[NMAX+10], stiva[NMAX+10], vf, nrctc;
vector <int> nod[NMAX+10], tnod[NMAX+10], ctc[NMAX+10];

void dfs1(int x)
{	viz[x] = 1;
	for(auto u : nod[x])
		if(!viz[u])
			dfs1(u);
	stiva[++vf] = x;
}

void dfs2(int x)
{	ctc[nrctc].push_back(x);
	viz[x] = 1;
	for(auto u : tnod[x])
		if(!viz[u])
			dfs2(u);
}

int main()
{
	fin >> n >> m;
	for(int i=1; i<=m; i++)
		{	int nod1, nod2;
			fin >> nod1 >> nod2;
			nod[nod1].push_back(nod2);
			tnod[nod2].push_back(nod1);
		}
	for(int i=1; i<=n; i++)
		if(!viz[i])
			dfs1(i);
	for(int i=1; i<=n; i++)
		viz[i] = 0;
	for(int i=n; i; i--)
		{	int x = stiva[i];
			if(!viz[x])
				{	nrctc++;
					dfs2(x);
				}
		}
	fout << nrctc << '\n';
	for(int i=1; i<=nrctc; i++)
		{	for(auto u : ctc[i])
				fout << u << ' ';
			fout << '\n';
		}
	return 0;
}