#include <bits/stdc++.h>
 
using namespace std;

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

int n, m, st[100005], top, nr;
bitset <100005> viz;
vector <int> a[100005], t[100005];
vector <int> cc[100005];

void Dfs1(int x)
{
	viz[x] = 1;
	for (auto w : a[x])
		if (viz[w] == 0)
			Dfs1(w);
	st[++top] = x;
}

void Dfs2(int x)
{
	viz[x] = 0;
	for (auto w : t[x])
		if (viz[w] == 1)
			Dfs2(w);
	cc[nr].push_back(x);
}

int main()
{
	int i, x, y;
	fin >> n >> m;
	for (i = 1; i <= m; i++)
	{
		fin >> x >> y;
		a[x].push_back(y);
		t[y].push_back(x);
	}

	for (i = 1; i <= n; i++)
		if (viz[i] == 0)
			Dfs1(i);

	for (i = n; i >= 1; i--)
		if (viz[st[i]] == 1)
		{
			nr++;
			Dfs2(st[i]);
		}
	fout << nr << "\n";
	for (i = 1; i <= nr; i++)
	{
		for (auto w : cc[i])
			fout << w << " ";
		fout << "\n";
	}

	return 0;
}