#include<bits/stdc++.h>
#define inl inline
using namespace std;
typedef unsigned long long ll;
const int N=5e5+5,IB=1<<21; char IN[IB],*IS=IN+IB,*IT=IS,OU[IB],*OS=OU,*OT=OU+IB;
#define getchar() (IS==IT&&(IT=IN+fread(IS=IN,1,IB,stdin)),IS==IT?EOF:*IS++)
#define flush() (fwrite(OU,1,OS-OU,stdout),OS=OU)
#define putchar(x) (OS==OT&&flush(),*OS++=x)
random_device rd; mt19937 sd(rd()); uniform_int_distribution<ll> ud(0,ULLONG_MAX);
struct E {int n,v; }e[N*3];
int n,m,ec=1,h[N],g[N],df[N],lw[N]; ll a[N],b[N]; vector<int> c[N];
inl int Read()
{
	int s=0; char c; while(!isdigit(c=getchar()));
	for(;isdigit(c);c=getchar()) s=s*10+c-'0'; return s;
}
inl void Write(int x)
{
	int c=0,s[10]; do s[++c]=x%10; while(x/=10);
	while(c) putchar(s[c--]+'0'); putchar(' ');
}
namespace HA
{
	struct A {int n,u; ll w; }a[N+N]; const ll P=555559; int ac,h[P];
	inl void Init() {memset(h,0,sizeof(h)); ac=0; }
	inl void Ins(ll w,int u) {int t=w%P; a[++ac]={h[t],u,w}; h[t]=ac; }
	inl void Pop(ll w) {int t=w%P; --ac; h[t]=a[h[t]].n; }
	inl int Find(ll w) {for(int i=h[w%P];i;i=a[i].n) if(a[i].w==w) return a[i].u; return -1; }
}
inl void DFS1(int p,int fi)
{
	df[p]=lw[p]=++m; for(int i=h[p],v;i;i=e[i].n) if(i!=fi&&df[v=e[i].v]<df[p])
	{
		if(df[v]) {lw[p]=min(lw[p],df[v]); ll t=ud(sd); a[p]^=t; a[v]^=t; HA::Ins(t,1); }
		else e[++ec]={g[p],v}, g[p]=ec, DFS1(v,i^1), lw[p]=min(lw[p],lw[v]), lw[v]>df[p]&&(b[v]^=ud(sd));
	}
}
inl void DFS2(int p)
{
	for(int i=g[p];i;i=e[i].n) DFS2(e[i].v), a[p]^=a[e[i].v]; ~HA::Find(a[p])&&(b[p]^=ud(sd));
}
inl void DFS3(int p)
{
	int u=HA::Find(a[p]); ll t=ud(sd); ~u&&(b[p]^=t,b[u]^=t);
	HA::Ins(a[p],p); for(int i=g[p];i;i=e[i].n) DFS3(e[i].v); HA::Pop(a[p]);
}
inl void DFS4(int p)
{
	for(int i=g[p];i;i=e[i].n) b[e[i].v]^=b[p], DFS4(e[i].v);
}
int main()
{
	n=Read(); m=Read(); for(int i=1,x,y;i<=m;++i)
		e[++ec]={h[x=Read()+1],y=Read()+1}, h[x]=ec, e[++ec]={h[y],x}, h[y]=ec;
	m=0; for(int i=1;i<=n;++i) !df[i]&&(DFS1(i,0),e[++ec]={g[0],i},g[0]=ec);
	DFS2(0); HA::Init(); DFS3(0); DFS4(0); HA::Init(); ec=0;
	for(int i=1;i<=n;++i) HA::Find(b[i])==-1&&(HA::Ins(b[i],i),++ec);
	Write(ec); putchar('\n'); for(int i=1;i<=n;++i) c[HA::Find(b[i])].push_back(i-1);
	for(int i=1,t;i<=n;++i) if(!c[i].empty()) {Write(c[i].size()); for(int v:c[i]) Write(v); putchar('\n'); }
	flush();
}