#include<fstream>
#include<vector>
#define lim 100006
using namespace std;
 
 
ifstream f("ctc.in");
ofstream g("ctc.out");
vector<int>G[lim],T[lim],Solutie[lim];
int n,m,i,j,x,y,ctc,dim;
int viz[lim],Mark[lim],st[lim];
 
 
void DFP(int nod ) {
    viz[nod]=1;
     
    for(int i=0;i<G[nod].size();++i)
        if(!viz[G[nod][i]])
            DFP(G[nod][i]);
    st[++dim]=nod;
}
 
 
 
void DFM(int nod,int ctc){
     
    Mark[nod]=ctc;
     
     
    for(int i=0;i<T[nod].size();++i)
        if(!Mark[T[nod][i]])
            DFM(T[nod][i],ctc);
     
}
 
 
int main (){
     
    f>>n>>m;
     
    for(i=1;i<=m;i++){
        f>>x>>y;
        G[x].push_back(y);
        T[y].push_back(x);
    }
     
    for(i=1;i<=n;++i)
        if(!viz[i])
            DFP(i);
         
         
    for(;dim;st[dim--]=0){
         
        if(Mark[st[dim]]==0)
            DFM(st[dim],++ctc);
         
    }
 
    for(i=1;i<=n;++i)
        Solutie[Mark[i]].push_back(i);
    g<<ctc<<"\n";
     
     
    for(int i=1;i<=ctc;i++){
         
        for(int j=0;j<Solutie[i].size();++j)
             
            g<<Solutie[i][j]<<" ";
        g<<"\n";
    }
     
     
    return 0;
}