#include <fstream>
#include <vector>
using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");

const int N = 200001;
int n, viz_a[N], viz_b[N], sol[N], l, k;
vector<int>a[N], b[N], mat[N];

void dfs_a(int nod)
{
	viz_a[nod] = 1;
	for (auto i: a[nod])
		if (viz_a[i] == 0)
			dfs_a(i);
	sol[++l] = nod;
}
void dfs_b(int nod)
{
	viz_b[nod] = 1;
	for (auto i : b[nod])
		if (viz_b[i] == 0)
			dfs_b(i);
	mat[k].push_back(nod);
}
int main()
{
	int m, i, j, x, y;
	cin >> n >> m;
	for (i = 1; i <= m; i++)
	{
		cin >> x >> y;
		a[x].push_back(y);
		b[y].push_back(x);
	}
	for (i = 1; i <= n; i++)
	{
		if (viz_a[i] == 0)
			dfs_a(i);
	}
	for (i = l; i >= 1; i--)
	{
		if (viz_b[sol[i]] == 0)
		{
			k++;
			dfs_b(sol[i]);
		}
	}
	cout << k << "\n";
	for (i = 1; i <= n; i++)
	{
		for (j = 0; j < mat[i].size(); j++)
			cout << mat[i][j] << ' ';
		cout << "\n";
	}

	return 0;
}