#include<stdio.h>
#include<vector>
using namespace std;
FILE*f=fopen("ctc.in","r");
FILE*g=fopen("ctc.out","w");
int niv,nr,n,m,x,y,j,stv[100001],niv1[100001],nivmin[100001];
char viz[100001],viz1[100001];
vector <vector <int> > S ;
vector <int> v[100001];
inline int min(int a,int b){
	if(a<b)
		return a;
	return b;
	
}
void dfs(int nod){
	
	viz1[nod]=viz[nod]=1;
	niv1[nod]=nivmin[nod]=niv;
	++niv;
	for(int i=0;i<v[nod].size();++i)
		if(!viz[v[nod][i]])
		{
			stv[++j]=v[nod][i];
			dfs(v[nod][i]);
			nivmin[nod]=min(nivmin[nod],nivmin[v[nod][i]]);
		}else
			if(viz1[v[nod][i]])
				nivmin[nod]=min(nivmin[nod],nivmin[v[nod][i]]);
	if(niv1[nod]==nivmin[nod])
	{
		vector <int> sol;
		do
		{
			sol.push_back (stv[j]);
			viz1[stv[j]]=0;
			--j;
		}
		while(stv[j+1]!=nod);
		S.push_back (sol);	
		++nr;
	}

}
int main(){
	fscanf(f,"%d%d",&n,&m);
	for(int i=1;i<=m;++i){
		fscanf(f,"%d%d",&x,&y);
		v[x].push_back (y);
	}
	
	
	for(int i=1;i<=n;++i)
		if(!viz[i]){
			stv[++j]=i;
			dfs(i);
		}
	fprintf(g,"%d\n",nr);
	for(int i=0;i<nr;++i)
	{
		for(int j=0;j<S[i].size();++j)
			fprintf(g,"%d ",S[i][j]);
		fprintf(g,"\n");
	}
	
	
	fclose(g);
	fclose(f);
	return 0;
}