#define DM 100001
#include <fstream>
#include <set>
#include <vector>
using namespace std;

ifstream fi ("ctc.in");
ofstream fo ("ctc.out");
bool in_stack[DM], was_checked[DM];
int n, m, a, b, next_ctc, actc[DM], crsp[DM];
set <int> normalize;
vector <int> v[DM], s, rev[DM];

void dfs(int x, int comp) {
	// found cycle
	if (in_stack[x]) {
		int ctc = comp;
		if (!ctc)
			ctc = ++next_ctc;
		actc[x] = ctc;
		for (int i = s.size() - 1; i >= 0; --i) {
			if (s[i] == x)
				break;
			actc[s[i]] = ctc;
		}
		return;
	}
	// marked node
	was_checked[x] = 1;
	in_stack[x] = 1;
	s.push_back(x);
	// propagated the dfs
	for (auto i:v[x])
		dfs(i, actc[x]);
	in_stack[x] = 0;
	s.pop_back();
}

int main() {
	// next_ctc poate fi mai mare decat nr real de componente, in cazul in care
	// o componenta tare conexa e invaluita de o alta, asa ca am nevoie de o 
	// normalizare a numerelor corespunzatoare componentelor -- nu stiu cum altfel
	// sa repar chestia asta

	fi >> n >> m;
	for (int i = 1; i <= m; ++i) {
		fi >> a >> b;
		v[a].push_back(b);
	}
	for (int i = 1; i <= n; ++i)
		if (!was_checked[i])
			dfs(i, 0);
	for (int i = 1; i <= n; ++i)
		normalize.insert(actc[i]);
	next_ctc = 0;
	for (auto i:normalize)
		crsp[i] = ++next_ctc;
	for (int i = 1; i <= n; ++i)
		rev[crsp[actc[i]]].push_back(i);
	fo << next_ctc << '\n';
	for (int i = 1; i <= next_ctc; ++i) {
		for (auto j:rev[i])
			fo << j << ' ';
		fo << '\n';
	}
	return 0;
}