#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
const int NMAX = 100505;
int N, M;
vector<int> G[NMAX], GT[NMAX];

void read() {
	scanf("%d%d", &N, &M);
	int x, y;
	for (int i = 1; i <= M; i++) {
		scanf("%d%d", &x, &y);
		G[x].push_back(y);
		GT[y].push_back(x);
	}
}

void dfsNormalGraph(int node, vector<bool>& visited, vector<int>& sortedByExitTime) {
	visited[node] = true;
	for (auto& neighbour : G[node]) {
		if (!visited[neighbour]) {
			dfsNormalGraph(neighbour, visited, sortedByExitTime);
		}
	}

	sortedByExitTime.push_back(node);
}

void dfsTransposeGraph(int node, vector<bool>& visited, vector<int>& currentComponent) {
	visited[node] = true;
	currentComponent.push_back(node);
	for (auto& neighbour : GT[node]) {
		if (!visited[neighbour]) {
			dfsTransposeGraph(neighbour, visited, currentComponent);
		}
	}
}

void solve() {
	vector<int> sortedByExitTime;
	vector<bool> visited(N + 1, false);
	for (int node = 1; node <= N; node++) {
		if (!visited[node]) {
			dfsNormalGraph(node, visited, sortedByExitTime);
		}
	}
	reverse(sortedByExitTime.begin(), sortedByExitTime.end());

	visited.assign(N + 1, false);
	vector<vector<int>> result;
	for (auto node : sortedByExitTime) {
		if (!visited[node]) {
			vector<int> currentComponent;
			dfsTransposeGraph(node, visited, currentComponent);
			result.push_back(currentComponent);
		}
	}

	printf("%d\n", (int) result.size());
	for (auto& component : result) {
		for (auto& node : component) {
			printf("%d ", node);
		}
		printf("\n");
	}
}

int main() {
	freopen("ctc.in", "r", stdin);
	freopen("ctc.out", "w", stdout);

	read();
	solve();
	return 0;
}