#include<stdio.h>
#include<algorithm>
#include<vector>
#define lim 100001
#define pb push_back

using namespace std;

FILE*f=fopen("ctc.in","r");
FILE*g=fopen("ctc.out","w");

int nr,n,m,x,y,j,niv;
int stv[lim],Niv[lim],nivmin[lim];

char viz[lim],Viz[lim];

vector <vector <int> > S ;
vector <int> v[100001];

inline int min(int a,int b){
	if(a<b)return a;
	return b;
}

void stiva(int t){
	vector <int> sol;
	do{
		sol.pb(stv[j]);
		Viz[stv[j]]=0;
		j--;
	}
	while(stv[j+1]!=t);
	S.pb(sol);	
	nr++;
}

void dfs(int nod){
	
	niv++;
	Viz[nod]=viz[nod]=1;
	Niv[nod]=nivmin[nod]=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(Viz[v[nod][i]]){
				nivmin[nod]=min(nivmin[nod],nivmin[v[nod][i]]);
			}
	}
	
	if(Niv[nod]==nivmin[nod]){
		stiva(nod);
	}
}


int main(){
	fscanf(f,"%d%d",&n,&m);
	for(int i=1;i<=m;++i){
		fscanf(f,"%d%d",&x,&y);
		v[x].pb(y);
	}
	for(int i=1;i<=n;i++){
		if(viz[i]==0){
			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(f);
	fclose(g);
	return 0;
}