#include <iostream>
#include<fstream>
using namespace std;
int n,m,a,b,i,viz1[50003],viz2[50003],j,ok=0,nrc=0;
struct nod
{
    int v;
    nod *urm;
}*p,*LA[50003], *LB[50003];
void dfa(int vf)
{
    nod *p;
    viz1[vf]=1;
    for(p=LA[vf];p;p=p->urm)
    {
        if(viz1[p->v]==0)
            dfa(p->v);
    }
}
void dfb(int vf)
{
    nod *p;
    viz2[vf]=1;
    for(p=LB[vf];p;p=p->urm)
    {
        if(viz2[p->v]==0)
            dfb(p->v);
    }
}
int main()
{
    ifstream fin("ctc.in");
    ofstream fout("ctc.out");
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>a>>b;
        p=new nod;
        p->v=b;
        p->urm=LA[a];
        LA[a]=p;
        p=new nod;
        p->v=a;
        p->urm=LB[b];
        LB[b]=p;
    }
for(i=1;i<=n;i++)
{
    if(viz1[i]==0)
    {
	nrc++;
        dfa(i);
        dfb(i);
        for(j=1;j<=n;j++)
        {
            if(viz1[j]==1 && viz2[j]==1)
            {
                viz1[j]=1+nrc;
                viz2[j]=1+nrc;
            }
            else
            {
               if(viz1[j]+viz2[j]==1) 
		{
		   viz1[j]=0;
		   viz2[j]=0;
		}
            }
        }
    }
}
fout<<nrc<<"\n";
for (i=1;i<=nrc;i++)
{
   for (j=1;j<=n;j++)
   	if(viz1[j]==1+i)fout<<j<<" ";
   fout<<"\n";
}
fout.close();
return 0;
}