#include<fstream>
#include<vector>
#include<stack>

using namespace std;
ifstream cin("ctc.in");
ofstream cout("ctc.out");
stack < int > S;
vector<int> G[100005], GT[100005], CTC[100005];
int N, M, NrCTC;
int beenThere[100005];
void Read()
{
    cin >> N >> M;
    for (int i = 1; i <= M; i++)
    {
        int x, y;
        cin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}
void DFSP(int Nod)
{
    beenThere[Nod] = 1;
    for (unsigned int i = 0; i < G[Nod].size(); i++)
    {
        int Vecin = G[Nod][i];
        if (!beenThere[Vecin])
            DFSP(Vecin);
    }
    S.push(Nod);
}
void DFSM(int Nod)
{
    beenThere[Nod] = 2;
    CTC[NrCTC].push_back(Nod);
    for (unsigned int i = 0; i < GT[Nod].size(); i++)
    {
        int Vecin = GT[Nod][i];
        if (beenThere[Vecin] == 1)
            DFSM(Vecin);
    }
}
void Solve()
{
    for (int i = 1; i <= N; i++)
        if (!beenThere[i])
            DFSP(i);
    while (!S.empty())
    {
        int Nod = S.top();
        if (beenThere[Nod] == 1)
        {
            NrCTC++;
            DFSM(Nod);
        }
        S.pop();
    }
}
void Print()
{
    cout << NrCTC << "\n";
    for (int i = 1; i <= NrCTC; i++)
    {
        for (unsigned int j = 0; j < CTC[i].size(); j++)
            cout << CTC[i][j] << " ";
        cout << "\n";
    }
}
int main()
{
    Read();
    Solve();
    Print();
    return 0;
}