#include <iostream>
#include <fstream>
#include <vector>
#define Nmax 100001
using namespace std;
int n,m;
vector < int > G[Nmax],GT[Nmax],conex[Nmax];
int nr;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int use[Nmax];
void lesen()
{
    fin>>n>>m;
    int i;
    for(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 k=0;k<G[nod].size();k++)
        if(use[G[nod][k]]==0)

            DFSP(G[nod][k]);

}

void DFSM(int nod)
{

    use[nod]=2;
    conex[nr].push_back(nod);
    for(unsigned int k=0;k<GT[nod].size();k++)
        if(use[GT[nod][k]]==1)

            DFSM(GT[nod][k]);

}

void losung()
{
    int i;
    for(i=1;i<=n;i++)

        if(use[i]==0)
    {

        nr++;
        DFSP(i);
        DFSM(i);
        for(int j=1;j<=n;j++)
            if(use[j]==1) use[j]=0;

    }


}
int main()
{
    lesen();
    losung();
    fout<<nr<<"\n";
    int i;
    for(i=1;i<=nr;i++)
    {
        for(unsigned int k=0;k<conex[i].size();k++)
            fout<<conex[i][k]<<" ";
        fout<<"\n";
    }
    return 0;
}