#include <bits/stdc++.h>
#define NMAX 100004

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

int n, m, ctc;
bool viz[NMAX];
vector <int> G[NMAX], GT[NMAX], sol[NMAX], post_ordine;

void citire();
void DFS(int nod);
void DFST(int nod);
void afisare();

int main()
{
    citire();
    for (int i = 1; i <= n; i++)
        if (!viz[i])
            DFS(i);
    for (int i = post_ordine.size() - 1; i >= 0; i--)
    {
        int val = post_ordine[i];
        if (viz[val])
        {
            ctc++;
            DFST(val);
        }
    }
    afisare();
    return 0;
}

void citire()
{
    int x, y;
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void DFS(int nod)
{
    viz[nod] = 1;
    for (int i = 0; i < G[nod].size(); i++)
    {
        int vf = G[nod][i];
        if (!viz[vf])
            DFS(vf);
    }
    post_ordine.push_back(nod);
}

void DFST(int nod)
{
    viz[nod] = 0;
    sol[ctc].push_back(nod);
    for (int i = 0; i < GT[nod].size(); i++)
    {
        int vf = GT[nod][i];
        if (viz[vf])
            DFST(vf);
    }
}

void afisare()
{
    fout << ctc << '\n';
    for (int i = 1; i <= n; i++)
    {
        for (int j = 0; j < sol[i].size(); j++)
            fout << sol[i][j] << ' ';
        fout << '\n';
    }
}