#include <iostream>
#include <fstream>
using namespace std;
 
ifstream fin("ctc.in");
ofstream fout("ctc.out");
 
struct Nod{int inf; Nod* leg;};
typedef Nod* nod;
 
nod a[100000],b[100000],s;
 
int n,m, viz[5001],viz2[5001];
 
void adaug(nod q, int x)
{
    nod p=new Nod;
    p->inf=x;
    p->leg=q;
    q=p;
}
 
void parc(int i)
{
    viz[i]=1;
    for(nod j=a[i]; j; j=j->leg) 
       if (!viz[j->inf])
        { parc(j->inf);adaug(s,j->inf);}
}
 
void parc2(int i)
{
    viz2[i]=k;
    for(nod j=b[i]; j; j=j->leg) if (!viz2[j->inf]) parc2(j->inf);
}
 
int main()
{
    int i,j,x,y,k=0;
    fin>>n>>m;
    for(i=1; i<=m; i++)
    {
        fin>>x>>y;
        adaug(a[x],y);
        adaug(b[y],x);
    }
    for(i=1; i<=n; i++)
        if(!viz[i])
            parc(i);
         while(s){
If (!viz[s->inf]){parc2(s->inf); k++;} s=s->leg;}
    fout<<k<<"\n";
    for(i=1; i<=k; i++)
    {
        for(j=1; j<=n; j++) if (viz[j]==i) fout<<j<<" ";
        fout<<"\n";
    }
 
    return 0;
}