#include <iostream>
#include <fstream>
#include <deque>
#include <set>
#include <algorithm>
#include <stack>
#include <vector>

#define MAX 100005

using namespace std;

ifstream fin("a.in");
ofstream fout("a.out");

stack<int> S;

vector<int> G[MAX], GT[MAX], CTC[MAX];

int N, M, nrCTC;
int checked[MAX];

void Read() {
	fin >> N >> M;

	for (int i = 1; i <= M; ++i) {
		int x, y;
		fin >> x >> y;
		G[x].push_back(y);
		GT[y].push_back(x);
	}
}

void DFSP(int nod) {
	checked[nod] = 1;

	for (int i = 0; i < G[nod].size(); ++i) {
		int vecin = G[nod][i];

		if (!checked[vecin])
			DFSP(vecin);
	}
	S.push(nod);
}

void DFSM(int nod) {
	checked[nod] = 2;
	CTC[nrCTC].push_back(nod);

	for (int i = 0; i < GT[nod].size(); ++i) {
		int vecin = GT[nod][i];

		if (checked[vecin] == 1)
			DFSM(vecin);
	}
}

void Solve() {
	for (int i = 1; i <= N; ++i)
		if (!checked[i])
			DFSP(i);

	while (!S.empty()) {
		int nod = S.top();
		if (checked[nod] == 1) {
			nrCTC++;
			DFSM(nod);
		}
		S.pop();
	}
}

void Print() {
	fout << nrCTC << " ";

	for (int i = 1; i <= nrCTC; ++i) {
		for (unsigned int j = 0; j < CTC[i].size(); ++j)
			fout << CTC[i][j] << " ";
		fout << "\n";
	}
}

int main() {

	Read();
	Solve();
	Print();

	return 0;
}