#include <fstream>
#include <vector>
#include <stack>

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,niv[MaxN],ind,low[MaxN],inS[MaxN];
vector<int> G[MaxN],c;
vector< vector<int> > C;
stack<int> S;

void DFS(int nod)
{
	S.push(nod);
	low[nod]=niv[nod]=++ind;
	inS[nod]=1;
	for(vector<int>::iterator it=G[nod].begin();it!=G[nod].end();++it)
	{
		if(!niv[*it])
		{
			DFS(*it);
			low[nod]=min(low[nod],low[*it]);
		}
		else
		{
			if(inS[*it])
			{
				low[nod]=min(low[nod],low[*it]);
			}
		}
	}

	if(low[nod]==niv[nod])
	{
		int x;
		c.clear();
		do
		{
			x=S.top();
			S.pop();
			inS[x]=0;
			c.push_back(x);
		}while(x!=nod);
		C.push_back(c);
	}
}

int main()
{
	fin>>N>>M;
	for(register int i=1;i<=M;++i)
	{
		fin>>x>>y;
		G[x].push_back(y);
	}
	fin.close();

	for(register int i=1;i<=N;++i)
	{
		if(!niv[i])
		{
			DFS(i);
		}
	}

	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;
}