#include<fstream>
#include<vector>
#define NMAX 100001

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

vector<int> adjList[NMAX], adjTrList[NMAX], ordList, component;
bool isVisited[NMAX];
bool isVisitedTr[NMAX];
vector<vector<int>> result;

void dfs(int startNode) {
	isVisited[startNode] = true;

	for (const auto& node : adjList[startNode]) {
		if (!isVisited[node]) {
			dfs(node);
		}
	}
	ordList.push_back(startNode);
}

void dfsTr(int startNode) {
	isVisitedTr[startNode] = true;
	component.push_back(startNode);

	for (const auto& node : adjTrList[startNode]) {
		if (!isVisitedTr[node]) {
			dfsTr(node);
		}
	}
}

int main() {

	int N, M;

	in >> N >> M;
	for (int i = 0; i < M; ++i) {
		int startNode, endNode;
		in >> startNode >> endNode;
		adjList[startNode].push_back(endNode);
		adjTrList[endNode].push_back(startNode);
	}

	for (int node = 1; node <= N; ++node) {
		if (!isVisited[node]) {
			dfs(node);
		}
	}

	int stronglyConnComp = 0;
	for (int i = 1; i <= N; ++i) {
		int node = ordList[N - i];
		if (!isVisitedTr[node]) {
			++stronglyConnComp;
			dfsTr(node);
			result.push_back(component);
			component.clear();
		}
	}

	out << stronglyConnComp << '\n';
	for (const auto& resultComponent: result) {
		for (const auto& node : resultComponent) {
			out << node << ' ';
		}
		out << '\n';
	}

	return 0;
}