#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, low[MaxN], niv[MaxN], S[MaxN], index, inS[MaxN];
vector<int> G[MaxN], comp;
vector< vector<int> > sol;

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

	if (low[nod] == niv[nod])
	{
		comp.clear();
		do
		{
			inS[S[S[0]]] = 0;
			comp.push_back(S[S[0]]);
			--S[0];
		} while (S[S[0]+1] != nod);
		sol.push_back(comp);
	}
}

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])
		{
			Tarjan(i);
		}
	}

	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;
}