#include <fstream>
#include <vector>
#include <cstring>
#define NMax 100005
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int N,M,O[NMax],K,NRC;
vector <int> G[NMax],GT[NMax],CTC[NMax];
bool Use[NMax];
void Read()
{
    fin>>N>>M;
    for(int i=1;i<=M;i++)
        {
            int x,y;
            fin>>x>>y;
            G[x].push_back(y);
            GT[y].push_back(x);
        }
}
void DFP(int Nod)
{
    Use[Nod]=1;
    for(unsigned int i=0;i<G[Nod].size();i++)
        {
            int Vecin=G[Nod][i];
            if(!Use[Vecin])
                DFP(Vecin);
        }
    O[++K]=Nod;
}

void DFM(int Nod)
{
    Use[Nod]=1;CTC[NRC].push_back(Nod);
    for(unsigned int i=0;i<GT[Nod].size();i++)
        {
            int Vecin=GT[Nod][i];
            if(!Use[Vecin])
                DFM(Vecin);
        }
}

void Kosaraju()
{
    for(int i=1;i<=N;i++)
        {
            if(!Use[i])
                DFP(i);
        }
    memset(Use,0,sizeof(Use));
    for(int i=K;i>=1;i--)
        {
            if(!Use[O[i]])
            {
                NRC++;
                DFM(O[i]);
            }

        }
}
void Print()
{
    fout<<NRC<<"\n";
    for(int i=1;i<=NRC;i++)
    {
        for(unsigned int j=0;j<CTC[i].size();j++)
            fout<<CTC[i][j]<<" ";
        fout<<'\n';
    }
}
int main()
{
    Read();
    Kosaraju();
    Print();
    return 0;
}