#include <fstream>
#include <vector>

using namespace std;

int n, m, x, y, st[100001], comp, l;
bool viz[100001];
vector<int>v[100001], vt[100001], ctc[100001];

void dfs (int nod) {
	vector<int>::iterator i;
	viz[nod] = 1;
	for (i = v[nod].begin(); i != v[nod].end(); i++)
		if (!viz[*i])
			dfs(*i);
	st[++l] = nod;
}

void dfst (int nod) {
	vector<int>::iterator i;
	viz[nod] = 1; ctc[comp].push_back(nod);
	for (i = vt[nod].begin(); i != vt[nod].end(); i++)
		if (!viz[*i])
			dfst(*i);
}

int main () {
	ifstream fi("ctc.in");
	ofstream fo("ctc.out");
	fi >> n >> m;
	for (int i = 1; i <= m; i++) {
		fi >> x >> y;
		v[x].push_back(y);
		vt[y].push_back(x);
	}
	for (int i = 1; i <= n; i++)
		if (!viz[i])
			dfs(i);
	for (int i = 1; i <= n; i++)
		viz[i] = 0;
	for (int i = n; i >= 1; i--)
		if (!viz[st[i]])
			comp++, dfst(st[i]);
	fo << comp << '\n';
	vector<int>::iterator j;
	for (int i = 1; i <= comp; i++) {
		for (j = ctc[i].begin(); j != ctc[i].end(); j++)
			fo << *j << ' ';
		fo << '\n';
	}
	return 0;
}