#include <fstream>
#include <vector>

using namespace std;

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

int N, M, nr, nrsol;
int postordine[100005];
vector<int> V[100005], W[100005], sol[100005];
bool used[100005];

void dfs(int nod)
{
    used[nod] = true;

    for (vector<int>::iterator it = V[nod].begin(); it != V[nod].end(); ++it)
        if (!used[*it])
            dfs(*it);

    postordine[++nr] = nod;
}

void dfsT(int nod)
{
    used[nod] = false;
    sol[nrsol].push_back(nod);

    for (vector<int>::iterator it = W[nod].begin(); it != W[nod].end(); ++it)
        if (used[*it])
            dfsT(*it);
}

int main()
{
    fin >> N >> M;
    for (int i = 1, nod1, nod2; i <= M; ++i)
    {
        fin >> nod1 >> nod2;
        V[nod1].push_back(nod2);
        W[nod2].push_back(nod1); // graf transpus
    }

    for (int i = 1; i <= N; ++i)
        if (!used[i])
            dfs(i);

    for (int i = N; i >= 1; --i)
        if (used[postordine[i]])
        {
            ++nrsol;
            dfsT(postordine[i]);
        }

    fout << nrsol << '\n';
    for (int i = 1; i <= nrsol; ++i)
    {
        for (vector<int>::iterator it = sol[i].begin(); it != sol[i].end(); ++it)
            fout << *it << ' ';
        fout << '\n';
    }

    fin.close();
    fout.close();
    return 0;
}