/*
 * PA 2010
 * Laborator 7 - Aplicatii DFS
 *
 * Determinarea componentelor tare conexe
 *
 */

#include <cstdio> // printf, scanf
#include <iostream>
#include <fstream>
#include <vector>               
#include <stack>

using namespace std;

#define min(a, b) ((a) < (b) ? (a) : (b))
 
typedef vector<int> *graf_t; 
 
int n, m;
graf_t G; // lista de adiacenta si transpusa
stack<int> S;
vector <vector<int> > sol;

int Index = 0;
int *idx, *lowlink;
bool *onstack;

void read_data(const char *filename)
{
	ifstream fin;
	int x, y;
	fin.open(filename);
	fin >> n >> m;
	G = new vector<int>[n];
	for (int i = 0; i < m; i++) {
		fin >> x >> y;
		x--; y--; // Indexare de la 0
		G[x].push_back(y);
	}
}

/* Tarjan */
void tarjan(int v)
{
	idx[v] = Index;
	lowlink[v] = Index;
	Index++;
	S.push(v);
	onstack[v] = true;
	for (size_t i = 0; i < G[v].size(); i++) {
		int u = G[v][i];
		if (idx[u] == -1) {
			tarjan(u);
			lowlink[v] = min(lowlink[v], lowlink[u]);
		}
		else if (onstack[u])
			lowlink[v] = min(lowlink[v], idx[u]);
	}
	if (lowlink[v] == idx[v]) {  // radacina unei CTC
		vector<int> temp;
		int u;
		do {
			u = S.top();
			S.pop();
			onstack[u] = false;
			temp.push_back(u);
		} while (u != v);
		sol.push_back(temp);
	}
}

void ctc_tarjan()
{
	Index = 0;
	idx = new int[n];
	lowlink = new int[n];
	onstack = new bool[n];
	for (int v = 0; v < n; v++) {
		idx[v] = -1;
		onstack[v] = false;
	}
	for (int v = 0; v < n; v++)
		if (idx[v] == -1) 
			tarjan(v);
}

void print_sol(const char *filename)
{
	ofstream fout;
	fout.open(filename);
	fout << sol.size() << endl;
	for (size_t i = 0; i < sol.size(); i++) {
		for (size_t j = 0; j < sol[i].size(); j++)
			fout << sol[i][j] + 1 << " ";
		fout << endl;
	}
	fout.close();
}

int main()
{   
    read_data("ctc.in");
	ctc_tarjan();
	print_sol("ctc.out");
	return 0;
}