#include <fstream>
#include <vector>

using namespace std;

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

const int Nmax = 100005;

int n, m, x, y, nr, k;
bool viz[Nmax];
int postordine[Nmax];
vector <int> A[Nmax], T[Nmax], rez[Nmax];

void DFS (int nod)
{
    viz[nod] = 1;

    for (auto i = 0; i < A[nod].size(); i++)
        if (!viz[A[nod][i]])
            DFS(A[nod][i]);
    postordine[++nr] = nod;
}

void DFST (int nod)
{
    viz[nod] = 0;
    rez[nr].push_back(nod);

    for (auto i = 0; i < T[nod].size(); i++)
        if (viz[T[nod][i]])
            DFST(T[nod][i]);
}

int main()
{
    in >> n >> m;

    for (int i = 1; i <= m; i++)
    {
        in >> x >> y;

        A[x].push_back(y);
        T[y].push_back(x);
    }

    for (int i = 1; i <= n; i++)
        if (!viz[i])
            DFS(i);

    nr = 0;

    for (int i = n; i >= 1; i--)
        if (viz[postordine[i]])
        {
            nr++;
            k = 0;
            DFST(postordine[i]);
        }

    out << nr << '\n';

    for (int i = 1; i <= nr; i++)
    {
        for (auto j = 0; j < rez[i].size(); j++)
        {
            out << rez[i][j] << ' ';
        }
        out << '\n';
    }

    return 0;
}