#include<bits/stdc++.h>
#include<bits/extc++.h>
using namespace std;
using namespace __gnu_pbds;
vector<pair<int,int>>g[500005],gg[500005];
int vist[500005];
#define ull unsigned long long
ull yy[500005],yh[500005],hh[500005],hy[500005],seed=13770617;
ull ran(){
	seed^=seed<<7;
	seed^=seed>>13;
	seed^=seed<<17;
	return seed;
}
int dep[500005];
void dfs0(int x,int la){
	vist[x]=1;
	for(auto pi:g[x]){
		int cu=pi.first,c2=pi.second;
		if(cu==c2)continue;
		if(vist[cu]){
			if(dep[cu]<dep[x]){
				yh[c2]=yy[c2];hh[cu]^=yy[c2];hh[x]^=yy[c2];
			}
			continue;
		}
		gg[x].emplace_back(cu,c2);
		dep[cu]=dep[x]+1;
		dfs0(cu,c2);
	}
}
int fa[500005],uu[500005],vv[500005],ok[500005],bg[500005],tot=0;
void dfs1(int x){
	bg[x]=++tot;
	for(auto pi:gg[x]){
		int cu=pi.first,c2=pi.second;
		fa[cu]=x;ok[c2]=1;
		dfs1(cu);
		yh[c2]^=hh[cu];
		hh[x]^=hh[cu];
	}
}
void dfs2(int x){
	for(auto pi:gg[x]){
		int cu=pi.first;
		hy[cu]^=hy[x];
		dfs2(cu);
	}
}
vector<int>gb[500005],g3[500005];
int main(){
	int n,m;
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;++i){
		int u,v;
		scanf("%d%d",&u,&v);
++u,++v;
		if(u==v)continue;
		g[u].emplace_back(v,i);
		g[v].emplace_back(u,i);
		uu[i]=u,vv[i]=v;
		yy[i]=ran();
	}
	vector<int>vc;
	for(int i=1;i<=n;++i)if(!vist[i]){
		dfs0(i,0);hy[i]^=ran();dfs1(i);
		vc.emplace_back(i);
	}
	gp_hash_table<ull,int>m1;
	for(int i=1;i<=m;++i){
		if(yh[i]==0){
			if(fa[uu[i]]==vv[i])swap(uu[i],vv[i]);
			hy[vv[i]]^=ran();
			continue;
		}
		if(!ok[i]){
			++m1[yh[i]];
		}
	}
	for(int i=1;i<=m;++i)if(yh[i]&&ok[i]){
		if(fa[uu[i]]==vv[i])swap(uu[i],vv[i]);
		if(m1[yh[i]]==1)hy[vv[i]]^=ran();
	}
	gp_hash_table<ull,int>m2;
	int tt=0;
	for(int i=1;i<=m;++i)if(yh[i]&&ok[i]){
		if(!m2[yh[i]])m2[yh[i]]=++tt;
		gb[m2[yh[i]]].emplace_back(i);
	}
	for(int i=1;i<=tt;++i){
		sort(gb[i].begin(),gb[i].end(),[&](int a,int b){
			return bg[vv[a]]<bg[vv[b]];
		});
		int sz=gb[i].size();
		if(sz<=1)continue;
		for(int j=0;j<sz-1;++j){
			int a=gb[i][j],b=gb[i][j+1];
			ull ul=ran();
			hy[vv[a]]^=ul,hy[vv[b]]^=ul;
		}
	}
	for(auto v:vc){
		dfs2(v);
	}
	gp_hash_table<ull,int>mp;
	int t=0;
	for(int i=1;i<=n;++i){
		if(!mp[hy[i]])mp[hy[i]]=i,++t;
		g3[mp[hy[i]]].emplace_back(i);
	}
	printf("%d\n",t);
	for(int i=1;i<=n;++i)if(g3[i].size()){
printf("%d ",(signed)g3[i].size());
		for(auto cu:g3[i])printf("%d ",cu-1);
		printf("\n");
	}
	return 0;
}