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

using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");

const int NIL = -1;
const int NMAX = 100001;
int n, m, index;
vector<int>low;
vector<int>disc;
vector<int>g[NMAX];
vector<int>inStack;
vector<vector<int>>sol;
stack<int>s;
void citire()
{

	cin >> n >> m;
	for (int i = 0; i < m; i++)
	{
		int x, y;
		cin >> x >> y;
		g[x].push_back(y);
	}
	cin.close();
}
void tarjan(int nod)
{	disc[nod] = low[nod] = index++;
	s.push(nod);
	inStack[nod] = 1;
	for(auto x:g[nod])
		if (disc[x] == NIL)
		{
			tarjan(x);
			low[nod] = min(low[x], low[nod]);
		}
		else if(inStack[x])
			low[nod] = min(disc[x], low[nod]);
	if (low[nod] == disc[nod])
	{
		vector<int>ctc;
		int nodAux=0;
		while (s.top() != nod)
		{
			nodAux = s.top();
			inStack[nodAux] = 0;
			s.pop();
			ctc.push_back(nodAux);
		}
		nodAux = s.top();
		inStack[nodAux] = 0;
		s.pop();
		ctc.push_back(nodAux);
		sol.push_back(ctc);
	}
}
void solve()
{
	low.resize(n + 1, NIL);
	disc.resize(n + 1, NIL);
	inStack.resize(n + 1, 0);
	for (int i = 1; i <= n; i++)
		if (disc[i]==NIL)
			tarjan(i);
}
void print()
{
	cout << sol.size() << '\n';
	for (int i = 0; i < sol.size(); i++,cout << '\n')
		for (int j = 0; j < sol[i].size(); j++)
			cout << sol[i][j] << ' ';
}
int main()
{
	citire();
	solve();
	print();
	return 0;
}