#include<fstream>
#include<vector>
#include<algorithm>

using namespace std;


vector <int> lvg[100001];
vector <int> lvgt[100001];
int d[100001];

int n,m,t;

int timp[100001],viz[100001];
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector <int> comp[100001];
 
void dfs(int nod)
{
	t++;
	viz[nod]=1;
	int j,s;
	s=lvg[nod].size()-1;
	
	for(j=0;j<=s;j++)
		if(!viz[lvg[nod][j]])dfs(lvg[nod][j]);
	t++;
	timp[nod]=t;
}
void dfs2(int nod)
{
	viz[nod]=1;
	int j,s;
	comp[t].push_back(nod);
	s=lvgt[nod].size()-1;
	
	for(j=0;j<=s;j++)
		if(!viz[lvgt[nod][j]])dfs2(lvgt[nod][j]);
}

bool cmp(int i,int j)
{ 
	return timp[i]>timp[j];
}

int main()
{
	
	int x,y,i;
	
	fin>>n>>m;
	
	for(i=1;i<=m;i++)
		{
			fin>>x>>y;
			lvg[x].push_back(y);
			lvgt[y].push_back(x);
		}
	for(i=1;i<=n;i++)
		if(!viz[i])dfs(i);
		
	
	
	for(i=1;i<=n;i++)
		{
			d[i]=i;
			viz[i]=0;
		}
	sort(d+1,d+n+1,cmp);
	t=0;
	
	for(i=1;i<=n;i++)
		{
			
			if(!viz[d[i]])
			{
				++t;
				dfs2(d[i]);
			}
		}	
	
	
	
	fout<<t<<"\n";
	for(i=1;i<=t;i++)
	{
		for(int j=0;j<=comp[i].size()-1;j++)
			fout<<comp[i][j]<<" ";
		fout<<"\n";
	}
	return 0;
}