#include <fstream>
#include <vector>
using namespace std;
const int NMAX=100001;
int n,m;
vector<int> G[NMAX],T[NMAX],c[NMAX];
int st[NMAX],sti,nc;
bool use[NMAX];
void dfsg(int nod)
{
	use[nod]=1;
	for(size_t i=0;i<G[nod].size();++i)
	{
		int vecin=G[nod][i];
		if(!use[vecin])
			dfsg(vecin);
	}
	st[sti++]=nod;
}
void dfst(int nod)
{
	use[nod]=0;
	c[nc].push_back(nod);
	for(size_t i=0;i<T[nod].size();++i)
	{
		int vecin=T[nod][i];
		if(use[vecin])
			dfst(vecin);
	}
}
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int main()
{
	int i,x,y;
	fin>>n>>m;
	while(m--)
	{
		fin>>x>>y;
		G[x].push_back(y);
		T[y].push_back(x);
	}
	for(i=1;i<=n;++i)
		if(!use[i])
			dfsg(i);
	while(sti--)
		if(use[st[sti]])
		{
			++nc;
			dfst(st[sti]);
		}
	fout<<nc<<"\n";
	for(i=1;i<=nc;++i)
	{
		for(size_t j=0;j<c[i].size();++j)
			fout<<c[i][j]<<" ";
		fout<<"\n";
	}
	return 0;
}