#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>


typedef std::vector<int>::iterator iter;
typedef std::vector<int>::reverse_iterator riter;


const int MAXN = 100005;
const int MAXM = 200005;
std::ifstream f("ctc.in");
std::ofstream g("ctc.out");
std::vector<int> G[MAXN]; int n, m;
std::vector<int> GT[MAXN];
std::bitset<MAXN> viz;
std::vector<int> order;
std::vector<int> comp;
std::vector< std::vector<int> > comps;


void topo(int node)
{
	if (viz[node] == true) {
		return;
	}
	viz[node] = true;
	for (iter it = G[node].begin(); it != G[node].end(); it++) {
		topo(*it);
	}
	order.push_back(node);
}


void buildComp(int node)
{
	if (viz[node] == true) {
		return;
	}
	viz[node] = true;
	for (iter it = GT[node].begin(); it != GT[node].end(); it++) {
		buildComp(*it);
	}
	comp.push_back(node);
}


int main()
{
	f >> n >> m;
	for (int i = 1, x, y; i <= m; i++) {
		f >> x >> y;
		G[x].push_back(y);
		GT[y].push_back(x);
	}


	for (int i = 1; i <= n; i++) {
		topo(i);
	}
	viz.reset();
	for (riter it = order.rbegin(); it != order.rend(); it++) {
		if (viz[*it] == true) {
			continue;
		}
		comp.clear();
		buildComp(*it);
		comps.push_back(comp);
	}

	g << comps.size() << std::endl;
	for (int i = 0; i < comps.size(); i++) {
		for (iter it = comps[i].begin(); it != comps[i].end(); it++) {
			g << *it << ' ';
		}
		g << '\n';
	}
	g.flush();


	//system("pause");
	f.close();
	g.close();
	return 0;
}