using namespace std;
#define NMax 100005
#include<fstream>
#include<vector>
#include<cstring>
#include<algorithm>
ifstream eu("ctc.in");
ofstream tu("ctc.out");
int N,M,K,Use[NMax];
vector <int> G[NMax],GT[NMax],List,CTC[NMax];

void Read()
{
eu>>N>>M;
while(M--)

	{
	int x,y;
	eu>>x>>y;
	G[x].push_back(y);
	GT[y].push_back(x);
	}
}

void DFP(int nod)
{
vector<int> :: iterator it;
Use[nod]=1;
for(it=G[nod].begin();it!=G[nod].end();it++)
	if(!Use[*it])
		DFP(*it);
List.push_back(nod);
}

void DFM(int nod)
{
vector <int> :: iterator it;
Use[nod]=1;CTC[K].push_back(nod);
for(it=G[nod].begin();it!=G[nod].end();it++)
	if(!Use[*it])
		DFM(*it);
}


void Solve()
{
int i;
vector<int> :: iterator it;
for(i=1;i<=N;i++)
	DFP(i);
reverse(List.begin(),List.end());
K=0;
memset(Use,0,sizeof(Use));
for(it=List.begin();it!=List.end();it++)
	if(!Use[*it])
	{
	K++;	
	DFM(*it);
	}
}
void Print()
{
vector<int> :: iterator it;
tu<<K<<"\n";
for(int i=1;i<=K;i++)
	{
	for(it=CTC[i].begin();it!=CTC[i].end();it++)
		tu<<*it<<" ";
	tu<<'\n';
	}
}
int main()
{
	Read();
	Solve();
	Print();
	return 0;
}