#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], comp;
vector< vector<int> > sol;

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)
{
	comp.push_back(nod);
	viz[nod] = 0;
	for (vector<int>::iterator it = GT[nod].begin(); it != GT[nod].end(); ++it)
	{
		if (viz[*it] == 1)
		{
			DFM(*it);
		}
	}
}

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();

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

	for (register int i = S[0]; i > 0; --i)
	{
		if (viz[S[i]] == 1)
		{
			comp.clear();
			DFM(S[i]);
			sol.push_back(comp);
		}
	}

	fout << sol.size() << "\n";
	for (vector< vector<int> >::iterator it = sol.begin(); it != sol.end(); ++it)
	{
		for (vector<int>::iterator elIt = it->begin(); elIt != it->end(); ++elIt)
		{
			fout << *elIt << " ";
		}
		fout << "\n";
	}
	fout.close();
	return 0;
}