#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

#define MAXN  100005

vector <int> Go[MAXN], Gi[MAXN], G[MAXN];

void read_in(vector <int>* Go, vector <int>* Gi, int& n)
{
	ifstream in("ctc.in");
	int cnt_edges, x, y;

	in >> n;
	for (in >> cnt_edges; cnt_edges > 0; --cnt_edges) {
		in >> x >> y;
		x--, y--;
		Go[x].push_back(y);
		Gi[y].push_back(x);
	}
	in.close();
}

vector <int> discovered, used;

void DFP(const int n, vector <int>* G)  // Marcheaza cu +
{
	vector <int>::iterator it;
	used[n] = true;
	for (it = G[n].begin(); it != G[n].end(); ++it)
		if (used[*it] == false)
			DFP(*it, G);
	discovered.push_back(n);
}

vector <int> where;

void DFM(const int n, vector <int> * G, const int which)  // Marcheaza cu -
{
	vector <int>::iterator it;
	where[n] = which;
	for (it = G[n].begin(); it != G[n].end(); ++it)
		if (where[*it] == -1)
			DFM(*it, G, which);
}

void print_out(const vector <int> * G, const int n)
{
	ofstream out("ctc.out");
	vector <int>::const_iterator it;

	out << n << endl;
	for (int i = 0; i < n; ++i) {
		for (it = G[i].begin(); it != G[i].end(); ++it)
			out << *it + 1 << " ";
		out <<endl;
	}
	out.close();
}


int main(void)
{
	int n;
	read_in(Go, Gi, n);

	used.resize(n);
	used.assign(used.size(), 0);
	for (int i = 0; i < n; ++i) if (used[i] == false)
		DFP(i, Go);

	where.resize(n);
	where.assign(where.size(), -1);
	int count = 0;
	for (; discovered.size(); discovered.pop_back())
		if (where[discovered.back()] == -1) {
			DFM(discovered.back(), Gi, count);
			count++;
		}
	for (int i = 0; i < n; ++i)
		G[where[i]].push_back(i);

	print_out(G, count);

	return 0;
}