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

using namespace std;

const char iname[] = "ctc.in";
const char oname[] = "ctc.out";

#define MAXN 100005

vector <int> adj[MAXN], con, idx, lowlink, in_stack;

vector < vector <int> > C;

stack <int> S;

int indecs;

void read_in(vector <int>* adj, int& n, const char iname[])
{
	ifstream in(iname);
	int cnt_edges, x, y;

	in >> n;
	for (in >> cnt_edges; cnt_edges > 0; --cnt_edges)
		in >> x >> y,
		adj[x - 1].push_back(y - 1);
	in.close();
}

void print_out(const vector < vector <int> >& G, const char oname[])
{
	ofstream out(oname);

	out << G.size() << "\n";
	for (size_t i = 0; i < G.size(); ++i) {
		for (size_t j = 0; j < G[i].size(); ++j)
			out << G[i][j] + 1 << " ";
		out << "\n";
	}
	out.close();
}

void tarjan(const int n, const vector <int>* adj)
{
	idx[n] = lowlink[n] = indecs;
	indecs++;
	S.push(n), in_stack[n] = 1;

	vector <int>::const_iterator it;
	for (it = adj[n].begin(); it != adj[n].end(); ++it) {
		if (idx[*it] == -1)
			tarjan(*it, adj),
			lowlink[n] = min(lowlink[n], lowlink[*it]);
		else if (in_stack[*it])
			lowlink[n] = min(lowlink[n], lowlink[*it]);
	}
	if (idx[n] == lowlink[n]) {
		con.clear();
		int node;
		do {
			con.push_back(node = S.top());
			S.pop(), in_stack[node] = 0;
		} while (node != n);
		C.push_back(con);
	}
}

int main(void)
{
	int n;
	read_in(adj, n, iname);

	idx.resize(n), lowlink.resize(n), in_stack.resize(n);
	idx.assign(n, -1), in_stack.assign(n, 0);
	for (int i = 0; i < n; ++i) if (idx[i] == -1)
		tarjan(i, adj);

	print_out(C, oname);

	return 0;
}