#include <fstream>
#include <vector>
#include <stack>
#define Nmax 100001
using namespace std;

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

int N, M, k, nrCTC;
int Viz[100001];
stack <int> St;
vector <int> G[Nmax], GT[Nmax], Raspuns[Nmax];

void Read()
{
    int x, y;
    fin >> N >> M;
    for (int i=1; i<=M; i++)
    {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}
void DFS(int Nod)
{
    Viz[Nod] = 1;
    for (unsigned int i=0; i<G[Nod].size(); i++)
    {
        int Vecin = G[Nod][i];
        if (Viz[Vecin] == 0)
        {
            DFS(Vecin);
        }
    }
    St.push(Nod);
}
void DFS_2(int Nod)
{
    Viz[Nod] = 2;
    Raspuns[nrCTC].push_back(Nod);
    for (unsigned int i=0; i<GT[Nod].size(); i++)
    {
        int Vecin = GT[Nod][i];
        if (Viz[Vecin] == 1)
        {
            DFS_2(Vecin);
        }
    }
}
void Solve()
{
    while (!St.empty())
    {
        int Nod = St.top();
        if (Viz[Nod] == 1)
        {
            nrCTC++;
            DFS_2(Nod);
        }
        St.pop();
    }
}
void Write()
{
    fout << nrCTC << '\n';
    for (int i=1; i<=nrCTC; i++)
    {
        for(unsigned int j = 0; j < Raspuns[i].size(); j++)
            fout << Raspuns[i][j] << " ";
        fout << '\n';

    }
}
int main()
{
    Read();
    for (int i=1; i<=N; i++)
        if (Viz[i] == 0)
            DFS(i);
    Solve();
    Write();
    return 0;
}