#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;

#define in "ctc.in"
#define out "ctc.out"
#define N 100005

vector <bool> d(N+1, 0);
vector <int> LIST[N], LISTT[N], O, C[N];
int n, m, c;

ofstream fout (out);

void DFS (int x)
{
	d[x] = 1;
	for (unsigned i = 0; i < LIST[x].size(); ++i)
		if (!d[LIST[x][i]])
			DFS (LIST[x][i]);
	O.push_back (x);
}

void DFST (int x)
{
	d[x] = 0;
	C[c].push_back (x);
	for (unsigned i = 0; i < LISTT[x].size(); ++i)
		if (d[LISTT[x][i]])
			DFST (LISTT[x][i]);
}

int main ()
{
	ifstream fin (in);
	fin >> n >> m;
	for (int i = 0; i < m; ++i) {
		int x, y;
		fin >> x >> y;
		LIST[x].push_back (y);
		LISTT[y].push_back (x);
	}
	fin.close();
	for (int i = 1; i <= n; ++i) {
		sort (LIST[i].begin(), LIST[i].end());
		sort (LISTT[i].begin(), LISTT[i].end());
	}
	for (int x = 1; x <= n; ++x)
		if (!d[x])
			DFS (x);
	for (int x = n-1; x >= 0; --x)
		if (d[O[x]]) {
			DFST (O[x]);
			c++;
		}
	ofstream fout (out);
	fout << c << "\n";
	for (int i = 0; i < c; ++i) {
		for (unsigned j = 0; j < C[i].size(); ++j)
			fout << C[i][j] << " ";
		fout << "\n";
	}
	return 0;
}