#include <fstream>
#include <iostream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

typedef struct graf {

	int x;
	graf* a;
}*L;

L a[100001];
L at[100001];
int stiva[100001];
int vf = 0;
int f[100001];
int ctc[100001];
int ctcord[100001];
int ans = 0;
vector <int> rez[100001];

int n, m;

void adaugare(L& dest, int val)
{
	L aux = new graf;
	aux->x = val;
	aux->a = dest;
	dest = aux;
}

void citire()
{
	int x, y;
	fin >> n >> m;
	for (int i = 1; i <= m; i++)
	{
		fin >> x >> y;
		adaugare(a[x], y);
		adaugare(at[y], x);
	}
}

void dfs1(int nod)
{
	f[nod] = 1;
	for (L p = a[nod]; p != NULL; p = p->a)
	{
		if (!f[p->x]) {
			dfs1(p->x);
		}
	}
	stiva[++vf] = nod;
}

void dfs2(int nod,int nrcomp)
{
	ctc[nod] = nrcomp;
	for (L p = at[nod]; p != NULL; p = p->a) {
		if (ctc[p->x]==0) {
			dfs2(p->x, nrcomp);
		}
	}
}

void Kosaraju() {
		
	for (int i = 1; i <= n; i++) {
		if (!f[i]) dfs1(i);
	}
	while (vf > 0)
	{
		int k = stiva[vf--];
		if (!ctc[k]) {
			ans++;
			dfs2(k, ans);
		}
	}
	//fout << ans;
}


void ordonare()
{
	int aux =1;
	for (int i = 1; i <= n; i++)
	{
		if (ctc[i] == ctc[i + 1]) {
			ctcord[i] = ctcord[i + 1] = aux;
		}
		else {
			aux++;
			ctcord[i + 1] = aux;
		}
	}
	fout << ans << '\n';
	for (int i = 1; i <= ans; i++)
	{
		for (int j = 1; j <= n; j++)
		{
			if (ctcord[j] == i) fout << j << ' ';
		}
		fout << '\n';
	}
}



void new_graf()
{
	Kosaraju();
	ordonare();
}

int main()
{
	citire();
	new_graf();
	
}