#include<fstream.h>
#include<vector>

using namespace std;

vector <int> v[100005],vt[100005],ctc[100005];
int timp[100005],sw[100005],nrc[100005],nr,swt[100005],n,m,nrctc,ID[100005];

ofstream g("ctc.out");

void afisare ()
{
	int i;
	vector <int > ::iterator it;
	g<<nrctc<<'\n';
	for (i=1;i<=nrctc;i++)
	{
		for (it=ctc[i].begin();it<ctc[i].end();it++)
			g<<*it<<' ';
		g<<'\n';
	}
	g.close();
}

void df2 (int i )
{
	vector <int> :: iterator  it;
	swt[i]=1;
	ctc[nrctc].push_back(i);
	for (it=vt[i].begin();it<vt[i].end();it++)
		if (!swt[*it])
			df2(*it);
}

void df (int i )
{
	vector <int> :: iterator it;
	sw[i]=1;
	for (it=v[i].begin();it<v[i].end();it++)
		if (!sw[*it])
			df(*it);
	timp[++nr]=i;
}

void comp()
{
	int i,j;
	nrctc=0;
	nr=0;
	for (i=1;i<=n;i++)
		if (!sw[i])
			df(i);
		
	for (j=nr;j;j--)
		if (!swt[timp[j]])
			{
			nrctc++;
			df2(timp[j]);
			}
}		

void citire ()
{
	int i,x,y;
	ifstream f("ctc.in");
	f>>n>>m;
	for (i=1;i<=m;i++)
	{
		f>>x>>y;
		v[x].push_back(y);
		vt[y].push_back(x);
	}
}

int main ()
{
	citire ();
	comp();
	afisare();
	return 0;
}