#include <fstream>
#include <vector>
#define NMAX 100002

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

int n, m, nrct, poz;
bool viz[NMAX];
int postordine[NMAX];

vector <int> g[NMAX];
vector <int> gt[NMAX];
vector <int> ctc[NMAX];

void citire();
void afisare();
void dfs(int x);
void dfst(int x);

int main()
{
    int i;

    citire();
    for(i = 1; i <= n; i++)
        if(viz[i] == false)
            dfs(i);

    for(i = n; i > 0; i--)
        if(viz[postordine[i]] == true)
        {
            nrct++;
            dfst(postordine[i]);
        }

    afisare();
    return 0;
}

void citire()
{
    int i, x, y;

    fin >> n >> m;
    for(i = 0; i < m; i++)
    {
        fin >> x >> y;

        ///y intra in lista de adiacenta a lui x in g
        g[x].push_back(y);

        ///x intra in lista de adiacenta a lui y in gt
        gt[y].push_back(x);
    }
}

void afisare()
{
    int i;

    fout << nrct << '\n';
    for(i = 1; i <= nrct; i++)
    {
        for(auto j : ctc[i])
            fout << j << ' ';
        fout << '\n';
    }
}

void dfs(int x)
{
    int i;
    ///parcurg lista de adiacenta a lui x
    viz[x] = true;
    for(i = 0; i < g[x].size(); i++)
        if(viz[g[x][i]] == false)
            dfs(g[x][i]);
    postordine[++poz] = x;
}

void dfst(int x)
{
    int i;
    viz[x] = false;
    ctc[nrct].push_back(x);
    for(i = 0; i < gt[x].size(); i++)
        if(viz[gt[x][i]] == true)
            dfst(gt[x][i]);
}