//g 	= graful
//gt 	= graful transpus
//dfs pe g
//dfst pe gt
//ctc 	= structura in care se afla componentele tare conexe

#include <stdio.h>
#include <string.h>
#include <vector>
#include <fstream>
#define maxN 131072

using namespace std;

int use[maxN];
int st[maxN];

vector <int> g[maxN];
vector <int> gt[maxN];
vector <int> ctc[maxN];
ifstream fis("ctc.in");
ofstream gfis("ctc.out");
int sol=0;

inline void dfs(int nod)
{
	use[nod]=1;
	for(int i=0;i<g[nod].size();++i)
		if(!use[g[nod][i]]) dfs(g[nod][i]);

	st[++st[0]]=nod;
}

inline void dfst(int nod)
{
	use[nod]=1;
	for(int i=0;i<gt[nod].size();++i)
		if(!use[gt[nod][i]]) dfst(gt[nod][i]);

	ctc[sol].push_back(nod);
}

int main(int argc,char *argv[])
{
	int n,m,x,y, i;

	 fis>>n>>m;
    for(i=1;i<=m;i++)
    { fis>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }




	memset(st,0,sizeof(st));
	memset(use,0,sizeof(use));

	for(int i=1;i<=n;++i)
		if(!use[i]) dfs(i);

	memset(use,0,sizeof(use));

	for(int i=n;i>0;--i)
		if(!use[st[i]])
	{
		++sol;
		dfst(st[i]);
	}

	gfis<<sol<<"\n";
	for(int i=1;i<=sol;++i)
	{
		for(int j=0;j<ctc[i].size();++j)
			gfis <<ctc[i][j]<<" ";
		gfis<<"\n";
	}

	return 0;
}