#include<fstream>
#include<string.h>
using namespace std;

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

typedef struct nod
{
	int inf;
	nod *urm;
} NOD;
typedef NOD *graf[100010];
graf G,T,C;

int n,m;
int v[100010],timp[100010],ordo[100010],t=1,nrc;

void citire()
{
	f>>n>>m;
	NOD *p;
	int a,b;
	for(int i=0;i<m;i++)
	{
		f>>a>>b;
		p=new NOD;
		p->inf=b;
		p->urm=G[a];
		G[a]=p;
		p=new NOD;
		p->inf=a;
		p->urm=T[b];
		T[b]=p;
	}
	f.close();
}

void timpFinal(int i)
{
	NOD *p=G[i];
	v[i]=1;
	while(p)
	{
		if(!v[p->inf])
		{
			timpFinal(p->inf);
			t++;
		}
		p=p->urm;
	}
	timp[i]=t;
}

void aranj()
{
	for(int i=1;i<=n;i++)
		ordo[n-timp[i]+1]=i;
}

void parcurg(int i)
{
	NOD *p=new NOD;
	v[i]=1;
	p->inf=i;p->urm=C[nrc];C[nrc]=p;
	p=T[i];
	while(p)
	{
		if(!v[p->inf])
			parcurg(p->inf);
		p=p->urm;
	}
}

int main()
{
	citire();
	timpFinal(1);
	aranj();
	memset(v,0,100001);
	for(int i=1;i<=n;i++)
	{
		if(!v[i])
		{
			nrc++;
			parcurg(i);
		}
	}
	g<<nrc<<'\n';
	for(int i=1;i<=nrc;i++)
	{
		NOD *p=C[i];
		while(p)
		{
			g<<p->inf<<' ';
			p=p->urm;
		}
		g<<'\n';
	}
	g.close();
	return 0;
}