#include <fstream>
#include <vector>

using namespace std;

const char InFile[]="ctc.in";
const char OutFile[]="ctc.out";
const int MaxN=100111;

ifstream fin(InFile);
ofstream fout(OutFile);

int N,M,x,y,viz[MaxN],S[MaxN];
vector<int> G[MaxN],GT[MaxN],c;
vector< vector<int> > C;

void DFP(int nod)
{
	viz[nod]=1;
	for(vector<int>::iterator it=G[nod].begin();it!=G[nod].end();++it)
	{
		if(!viz[*it])
		{
			DFP(*it);
		}
	}
	S[++S[0]]=nod;
}

void DFM(int nod)
{
	c.push_back(nod);
	viz[nod]=0;
	for(vector<int>::iterator it=GT[nod].begin();it!=GT[nod].end();++it)
	{
		if(viz[*it])
		{
			DFM(*it);
		}
	}
}

inline void Kosaraju()
{
	for(register int i=1;i<=N;++i)
	{
		if(!viz[i])
		{
			DFP(i);
		}
	}
	
	while(S[0])
	{
		int x=S[S[0]];
		if(viz[x])
		{
			c.clear();
			DFM(x);
			C.push_back(c);
		}
		--S[0];
	}
}

int main()
{
	fin>>N>>M;
	for(register int i=1;i<=M;++i)
	{
		fin>>x>>y;
		G[x].push_back(y);
		GT[y].push_back(x);
	}
	fin.close();
	
	Kosaraju();
	
	fout<<C.size()<<"\n";
	for(vector< vector<int> >::iterator it=C.begin();it!=C.end();++it)
	{
		for(vector<int>::iterator it2=it->begin();it2!=it->end();++it2)
		{
			fout<<*it2<<" ";
		}
		fout<<"\n";
	}
	fout.close();
	return 0;
}