#include<stdio.h>
#include<vector>
#define nmax 100005
using namespace std;
vector <int> l[nmax],lt[nmax],comp[nmax];
int v[nmax],p[nmax],n,m,nr,nrcomp;
void cit(){
	FILE *f;
	int a,b;
	f=fopen("ctc.in","r");
	fscanf(f,"%d%d",&n,&m);
	for(int i=1;i<=m;i++){
		fscanf(f,"%d%d",&a,&b);
		l[a].push_back(b);
		lt[b].push_back(a);
	}
	fclose(f);
}
void df(int k){
	v[k]=1;
	for(unsigned int i=0;i<l[k].size();i++)
		if(v[l[k][i]]==0)
			df(l[k][i]);
	nr++;
	p[nr]=k;
}
void dft(int k){
	v[k]=0;
	comp[nrcomp].push_back(k);
	for(unsigned int i=0;i<lt[k].size();i++)
		if(v[lt[k][i]])
			dft(lt[k][i]);
}
void afis(){
	FILE *f;
	f=fopen("ctc.out","w");
	fprintf(f,"%d\n",nrcomp);
	for(int i=1;i<=nrcomp;i++){
		for(unsigned int j=0;j<comp[i].size();j++)
			fprintf(f,"%d ",comp[i][j]);
		fprintf(f,"\n");
	}
	fclose(f);
}
int main(){
	cit();
	for(int i=1;i<=n;i++)
		if(v[i]==0)
			df(i);
	for(int i=n;i>=1;i--)
		if(v[p[i]]){
			nrcomp++;
			dft(p[i]);
		}
	afis();
	return 0;
}