#include <fstream>
#include <vector>
using namespace std;
ifstream in ("ctc.in");
ofstream out ("ctc.out");
const int NMax = 1e5+5;
int n,m,contor;
int Use[NMax],V[NMax], Nr;
vector <int> G[NMax];
vector <int> Sol[NMax];
vector <int> Gc [NMax];
void Read()
{
    in>>n>>m;
    int x,y;
    for (int i=0;i<m;i++)
    {
        in>>x>>y;
        G[x].push_back(y);
        Gc[y].push_back(x);
    }
}
void DfsG (int nod)
{
    Use[nod]=1;
    for (unsigned int i=0;i<G[nod].size();i++)
    {
        int vecin;
        vecin=G[nod][i];
        if (!Use[vecin])
            DfsG(vecin);
    }
    Nr++;
    V[Nr]=nod;
}
void DfsGc(int nod)
{
    Use[nod]=0;
    for (unsigned int i=0;i<Gc[nod].size();i++)
    {
        int vecin;
        vecin=Gc[nod][i];
        if (Use[vecin])
            DfsG(vecin);
    }
    Sol[contor].push_back(nod);
}
void Solve ()
{
    for (int i=1;i<=n;i++)
    {
        if (Use[i]==0)
        {
            DfsG(i);
        }
    }
    for (int i=n;i>0;i--)
    {
        if (Use[V[i]])
        {
            contor++;
            DfsGc(V[i]);
        }
    }
}
void Print()
{
    out<<contor<<'\n';
    for (int i=1;i<contor;i++)
    {
        for (int j=0;j<Sol[j].size();i++)
        {
            out<<Sol[i][j]<<' ';
        }
        out<<'\n';
    }
}
int main ()
{
    Read();
    Solve();
    Print();
}