#include <bits/stdc++.h>
#define nmax 100003
using namespace std;

vector<int> L[nmax]; /// liste ad
vector<int> T[nmax]; /// listele pe
/// graful transpus
int viz[nmax], s[nmax], n, m, len;
vector<int> ctc[nmax]; /// aici retinem
/// comp. tari conexe
int nrc; /// numarul de componente
         /// tari conexe

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

void Citire()
{
    int i, j, k;
    fin >> n >> m;
    for (k = 1; k <= m; k++)
    {
        fin >> i >> j;
        L[i].push_back(j);
        T[j].push_back(i);
    }
}

void DFS1(int k)
{
    viz[k] = 1;
    for (int i : L[k])
        if (viz[i] == 0) DFS1(i);
    s[++len] = k;
}

void SortTop()
{
    for (int k = 1; k <= n; k++)
        if (viz[k] == 0)
            DFS1(k);
}

void ReInit()
{
    for (int i = 1; i <= n; i++)
        viz[i] = 0;
}

void DFS2(int k)
{
    viz[k] = nrc;
    for (int i : T[k])
        if (viz[i] == 0) DFS2(i);
    ctc[nrc].push_back(k);
}

void Kosaraju()
{
    for (int k = n; k >= 1; k--)
        if (viz[s[k]] == 0)
        {
            nrc++;
            DFS2(s[k]);
        }
}

void Afisare()
{
    fout << nrc << "\n";
    for (int k = 1; k <= nrc; k++)
    {
        for (int i : ctc[k])
            fout << i << " ";
        fout << "\n";
    }
}

int main()
{
    Citire();
    SortTop();
    ReInit();
    Kosaraju();
    Afisare();
    return 0;
}