#include <fstream>
#include <vector>

using namespace std;

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

int n, m, l, nr;
bool vizitat[100001];
int q[100001];

vector <int> k[100001], k1[100001], sol[100001];

void DFS(int nod)
{
    int vecin;
    vizitat[nod] = 1;
    for (int i = 0; i < k[nod].size(); ++i)
    {
        vecin = k[nod][i];
        if (vizitat[vecin] == 0)
            DFS(vecin);
    }
    q[++q[0]] = nod;
}

void DFS1(int nod, int nr)
{
    int vecin;
    vizitat[nod] = 1;
    for (int i = 0; i < k1[nod].size(); ++i)
    {
        vecin = k1[nod][i];
        if (vizitat[vecin] == 0)
            DFS1(vecin, nr);
    }
    sol[nr].push_back(nod);
}

void citire()
{
    int x, y;
    in >> n >> m;
    for (int i = 1; i <= m; ++i)
    {
        in >> x >> y;
        k[x].push_back(y);
        k1[y].push_back(x);
    }
    for (int i = 1; i <= n; ++i)
    {
        if (vizitat[i] == 0)
            DFS(i);
    }
    for (int i = 1; i <= n; ++i)
        vizitat[i] = 0;
    nr = 0;
    for (int i = q[0]; i > 0; --i)
    {
        if (vizitat[q[i]] == 0)
            DFS1(q[i], ++nr);
    }
    out << nr << '\n';
    for (int i = 1; i <= nr; ++i)
    {
        for (int j = 0; j < sol[i].size(); ++j)
            out << sol[i][j] << " ";
        out << '\n';
    }
}

int main()
{
    citire();
    return 0;
}