#include <iostream>
#include <fstream>

using namespace std;

const int N = 200001;
int n, m, nr, s, nc, q[N], distances[N], c[N];
int vf[2 * N], vf1[2 * N], lst[N], lst1[N], urm[2 * N], urm1[2 * N];
bool viz[N], viz1[N];
int st[N], st1[N];
int varf;

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

void adauga(int x, int y) {
	vf[++nr] = y;
	urm[nr] = lst[x];
	lst[x] = nr;
	vf1[nr] = x;
	urm1[nr] = lst1[y];
	lst1[y] = nr;
}

void dfs(int x) {
	//cout << x << ' ';
	viz[x] = true;
	int y;
	for (int p = lst[x]; p != 0; p = urm[p]) {
		y = vf[p];
		if (!viz[y]) dfs(y);
	}
	st[++varf] = x;
}

void dfs1(int x) {
	viz1[x] = true;
	c[nc]++;   // cate varfuri are fiecare componenta conexa
	st1[++nr] = x;
	int y;
	for (int p = lst1[x]; p != 0; p = urm1[p]) {
		y = vf1[p];
		if (!viz1[y]) dfs1(y);
	}
}

struct comp {
	int x, y;
}v[N];


int main() {
	in >> n >> m;
	for (int i = 1; i <= m; i++) {
		in >> v[i].x >> v[i].y;
		adauga(v[i].x, v[i].y);
	}
	for (int i = 1; i <= n; i++)
		if (!viz[i]) dfs(i);
	nr = 0;
	for (int i = n; i >= 1; i--) {
		if (!viz1[st[i]]) {
			nc++;
			dfs1(st[i]);
		}
	}

	int a = 1;
	out << nc << '\n';
	for (int i = 1; i <= nc; i++) {
		for (int j = 1; j <= c[i]; j++)
			out << st1[a++] << ' ';
		out << '\n';
	}
	return 0;
}