#include <fstream>
#include <vector>
#include <bitset>
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

const int nmax = 50001;
int x, y, n, m, cnt, srt[nmax];
bitset<nmax> viz;
vector<int> v[nmax], g[nmax],conexe[nmax];


void dfs(int x)
{
	viz[x] = 1;
	for (int i = 0; i < v[x].size(); i++)
	{
		if (!viz[v[x][i]])
		{
			dfs(v[x][i]);
		}
	}
	srt[++cnt] = x;
}

void dfst(int x)
{
	conexe[cnt].push_back(x);
	viz[x] = 1;
	for (int i = 0; i < g[x].size(); i++)
	{
		if (!viz[g[x][i]])
		{
			dfst(g[x][i]);
		}
	}
}

int main()
{
	fin >> n >> m;
	for (; m; m--)
	{
		fin >> x >> y;
		v[x].push_back(y);
		g[y].push_back(x);
	}
	for (int i = 1; i <= n; i++)
	{
		if (!viz[i])
			dfs(i);
	}
	viz = 0;
	cnt = 0;
	for (int i = n; i >= 1; i--)
	{
		if (!viz[srt[i]])
		{
			cnt++;
			dfst(srt[i]);
		}
	}
	fout << cnt << '\n';
	for (int i = 1; i <= cnt; i++)
	{
		for (int j = 0; j < conexe[i].size(); j++)
		{
			fout << conexe[i][j] << ' ';
		}
		fout << '\n';
	}

}