#include <iostream>
#include <fstream>
#define nmax 100000
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,m,viz[nmax+5],sol[nmax/2],solu[nmax+5],t=0,u=0;
struct nod
{
    int info;
    nod *urm, *ante;
}*v[nmax+5],*c,*d,*ctc,*e,*w[nmax+5];
void adauga(int k)
{
    if(!ctc->urm)
    {
        d=new nod;
        d->urm=0;
        d->info=k;
        d->ante=ctc;
        ctc->urm=d;
        e=d;
    }
    else
    {
        d=new nod;
        d->urm=0;
        d->ante=e;
        d->info=k;
        e->urm=d;
        e=d;
    }
}
void dfs(int k,int caz)
{
    if(caz==1)
   {
       nod *gg;
       viz[k]=1;
       gg=v[k];
       while(gg->urm)
       {
            gg=gg->urm;
            if(!viz[gg->info])
                dfs(gg->info,caz);
       }
       adauga(k);
    }
    else
    {
        nod *gg;
        viz[k]=0;
        gg=w[k];
        while(gg->urm)
        {
            gg=gg->urm;
            if(viz[gg->info])
                dfs(gg->info,caz);
        }
        solu[++u]=k;
        sol[t]++;
    }
}
void tc(int caz)
{
    if(caz==1)
    for(int i=1;i<=n;i++)
        if(!viz[i])
        dfs(i,caz);
    if(caz==2)
    {
        c=e;
        while(c->ante)
        {
            if(viz[c->info])
            {
                t++;dfs(c->info,caz);
            }
            c=c->ante;
        }
    }
}
int main()
{
    int x,y;
    fin>>n>>m;
    for(int i=1;i<=n;i++)
    {
        v[i]=new nod;
        v[i]->info=i;
        v[i]->urm=0;
        w[i]=new nod;
        w[i]->info=i;
        w[i]->urm=0;
    }
    while(fin>>x>>y)
    {
        c=v[x];
        while(c->urm)
            c=c->urm;
        d=new nod;
        d->urm=0;
        d->info=y;
        d->ante=c;
        c->urm=d;
        c=w[y];
        while(c->urm)
            c=c->urm;
        d=new nod;
        d->urm=0;
        d->info=x;
        c->urm=d;
        d->ante=c;
    }
    ctc=new nod;
    ctc->urm=0;
    ctc->info=0;
    ctc->ante=0;
    tc(1);
    tc(2);
    fout<<t<<"\n";
    int j=1;
    for(int i=1;i<=t;i++)
    {
        x=j;
        while(j<x+sol[i])
        {
            fout<<solu[j]<<" ";
            j++;
        }
        fout<<"\n";
    }
    return 0;
}