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

void DFSM(int Nod)
{
    Use[Nod]=2;CTC[NRC].push_back(Nod);
    for(unsigned int i=0;i<GT[Nod].size();i++)
        {
            int Vecin=GT[Nod][i];
            if(Use[Vecin]==1)
                {
                    DFSM(Vecin);
                }
        }
}


void Solve()
{
    for(int i=1;i<=N;i++)
        if(!Use[i])
            DFSP(i);
    for(int i=k;i>=1;i--)
            if(Use[O[i]]==1)
                {
                    NRC++;
                    DFSM(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();
    Solve();
    Print();
    return 0;
}