// http://infoarena.ro/problema/ctc
// http://en.wikipedia.org/wiki/Tarjan's_strongly_connected_components_algorithm
#include <fstream>
#include <algorithm>
#include <list>
#include <stack>
using namespace std;

#define maxSize 100001

int nodes,counter,stronglyConnectedComponents;
int indexx[maxSize];	// retine ordinea in care au fost vizitate nodurile
int lowLink[maxSize];
bool inStack[maxSize];
list<int> graph[maxSize];
list< list<int> > solution;
stack<int> myStack;

void read();
void tarjan(int currentNode);
void write();

int main() {
	read();

	for(int i=1;i<=nodes;i++)
		if(!indexx[i])	// daca nu a fost vizitat
			tarjan(i);

	write();

	return (0);
}

void read() {
	ifstream in("ctc.in");
	int edges,from,to;

	in >> nodes >> edges;
	for(int i=1;i<=edges;i++) {
		in >> from >> to;

		graph[from].push_back(to);
	}

	in.close();
}

void tarjan(int currentNode) {
	indexx[currentNode] = ++counter;
	lowLink[currentNode] = counter;

	myStack.push(currentNode);	// se adauga in stiva nodul curent
	inStack[currentNode] = true;	// se marcheza ca fiind in stiva

	list<int>::iterator neighbour;
	for(neighbour=graph[currentNode].begin();neighbour!=graph[currentNode].end();neighbour++)
		if(!indexx[*neighbour]) {	// daca nu a fost vizitat
			tarjan(*neighbour);
			lowLink[currentNode] = min(lowLink[currentNode],lowLink[*neighbour]);
		}
		else
			if(inStack[*neighbour])
				lowLink[currentNode] = min(lowLink[currentNode],lowLink[*neighbour]);

	// daca s-a identificat o componenta tare-conexa
	if(lowLink[currentNode] == indexx[currentNode]) {
		int node = NULL;
		list<int> currentSolution;

		while(node != currentNode) {
			node = myStack.top();	// se extrage nodul din varful stivei
			myStack.pop();	// se elimina nodul extras
			inStack[node] = false;

			currentSolution.push_back(node);	// se adauga in solutia curenta
		}

		solution.push_back(currentSolution);	// se adauga solutia
		stronglyConnectedComponents++;	// creste numarul componentelor tare-conexe
	}
}

void write() {
	ofstream out("ctc.out");
	list< list<int> >::iterator first;
	list<int>::iterator second;

	out << stronglyConnectedComponents << "\n";

	for(first=solution.begin();first!=solution.end();first++) {
		for(second=first->begin();second!=first->end();second++)
			out << *second << " ";
		out << "\n";
	}

	out.close();
}