//ALEX ENACHE

#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <unordered_map>
#include <time.h>
#include <iomanip>
#include <deque>
#include <math.h>
#include <assert.h>
#include <stack>
#include <bitset>
#include <random>

using namespace std;

//-----------------------------------------------------------------

#include <fstream>

//ifstream cin("input"); ofstream cout("output");
ifstream cin("ctc.in"); ofstream cout("ctc.out");

const int inf = 1e9;
const int MAXN = 1e5 + 10;

vector < int > gr[MAXN];
vector < int > inv[MAXN];

int used[MAXN];

vector < int > ord;
vector < int > aux;
vector < vector < int > > ans;

void dfs(int nod) {
	used[nod] = 1;
	for (auto& x : gr[nod]) {
		if (!used[x]) {
			dfs(x);
		}
	}
	aux.push_back(nod);
}

int main() {

	int n, m;
	cin >> n >> m;

	while (m--) {
		int a, b;
		cin >> a >> b;
		gr[a].push_back(b);
		inv[b].push_back(a);
	}

	for (int i = 1; i <= n; i++) {
		if (!used[i]) {
			dfs(i);
			for (auto& x : aux) {
				ord.push_back(x);
			}
			aux.clear();
		}
	}

	reverse(ord.begin(), ord.end());

	for (int i = 1; i <= n; i++) {
		used[i] = 0;
		gr[i] = inv[i];
	}

	for (auto& x : ord) {
		if (!used[x]) {
			dfs(x);
			ans.push_back(aux);
			aux.clear();
		}
	}

	cout << ans.size() << '\n';
	for (auto& x : ans) {
		for (auto& y : x) {
			cout << y << " ";
		}
		cout << '\n';
	}


	return 0;
}