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

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

int n, m, nr, timp;
int low[100001], disc[100001];
bool viz[100001];
vector <int> g[100001], sol[100001];
stack <int> s;

inline void DFS(int nod)
{
	viz[nod] = 1;
	low[nod] = disc[nod] = ++timp;
	s.push(nod);
	for (int i = 0; i < g[nod].size(); ++i)
	{
		int vecin = g[nod][i];
		if (!disc[vecin])
		{
			DFS(vecin);
			low[nod] = min(low[nod], low[vecin]);
		}
		else if (viz[vecin])
			low[nod] = min(low[nod], disc[vecin]);
	}
	if (low[nod] == disc[nod])
	{
		++nr;
		while (s.top() != nod)
		{
			sol[nr].push_back(s.top());
			viz[s.top()] = 0;
			s.pop();
		}
		sol[nr].push_back(s.top());
		viz[s.top()] = 0;
		s.pop();
	}
}

inline void citire()
{
	int x, y;
	in >> n >> m;
	for (int i = 1; i <= m; ++i)
	{
		in >> x >> y;
		g[x].push_back(y);
	}
}

int main()
{
	citire();
	for (int i = 1; i <= n; ++i)
	{
		if (!disc[i])
			DFS(i);
	}
	out << nr << '\n';
	for (int i = 1; i <= nr; ++i)
	{
		for (int j = 0; j < sol[i].size(); ++j)
			out << sol[i][j] << " ";
		out << '\n';
	}
	return 0;
}