#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int N=2e6+5;
int n,m,dfn[N],low[N],tot1,tot2,col[N],cut[N];
struct edge{int to,id;};
vector<edge>v[N];
vector<int>g[N];
void dfs1(int x,int i){
	dfn[x]=low[x]=++tot1;
	for(edge e:v[x]){
		if(e.id==i) continue;
		if(!dfn[e.to]){
			dfs1(e.to,e.id);
		    low[x]=min(low[x],low[e.to]);
			if(low[e.to]>=dfn[x]) cut[e.id]=1;
		}
		else{
		    low[x]=min(low[x],dfn[e.to]);
		}
	}
}
void dfs2(int x){
	if(col[x]) return ;
	col[x]=tot2;
	g[tot2].push_back(x);
	for(edge e:v[x])
		if(!cut[e.id]) dfs2(e.to);
}
int main(){
	scanf("%d%d",&n,&m);
	for(int i=1,x,y;i<=m;i++){
		scanf("%d%d",&x,&y);
		x++,y++;
		v[x].push_back(edge{y,i});
		v[y].push_back(edge{x,i});
	}
	for(int i=1;i<=n;i++) if(!dfn[i]) dfs1(i,0);
	for(int i=1;i<=n;i++) if(!col[i]){
		tot2++;
		dfs2(i);
	}
	printf("%d\n",tot2);
	for(int i=1;i<=tot2;i++){
		printf("%d ",g[i].size());
		for(int e:g[i]) printf("%d ",e-1);
		puts("");
	}
	return 0;
}