#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
using namespace std;

int n,m,cnt=1,tm,tot;
int h[200005];
bool ok[200005];
int uu[200005];
int vv[200005];
int dfn[200005];
int low[200005];
bool vis[200005];
struct node{int v,nxt;}edge[400005];
vector <int> g[200005];

inline void addedge(int u,int v){
	edge[++cnt]={v,h[u]};
	h[u]=cnt;return ;
}

inline void in(int &n){
	n=0;
	char c=getchar();
	while(c<'0' || c>'9') c=getchar();
	while(c>='0'&&c<='9') n=n*10+c-'0',c=getchar();
	return ;
}

inline void tarjan(int u,int in){
	dfn[u]=low[u]=++tm;
	for(int i=h[u];i;i=edge[i].nxt){
		int v=edge[i].v;
		if(!dfn[v]){
			tarjan(v,i);
			if(dfn[u]<low[v])
				ok[i]=ok[i^1]=1;
			low[u]=min(low[u],low[v]);
		}
		else if(i!=(in^1)) low[u]=min(low[u],dfn[v]);
	}
	return ;
}

inline void dfs(int u){
	vis[u]=1;
	g[tot].emplace_back(u);
	for(int i=h[u];i;i=edge[i].nxt){
		if(ok[i]||vis[edge[i].v]) continue;
		dfs(edge[i].v);
	}
	return ;
}

int main(){
	in(n),in(m);
	for(int i=1;i<=m;i++){
		int u,v;
		in(u),in(v);
		u++,v++;
		uu[i]=u,vv[i]=v;
		addedge(u,v);
		addedge(v,u);
	}
	for(int i=1;i<=n;i++)
		if(!dfn[i]) tarjan(i,0);
	for(int i=1;i<=n;i++)
		if(!vis[i]) tot++,dfs(i);
	printf("%d\n",tot);
	for(int i=1;i<=tot;i++){
		printf("%d ",(int) g[i].size());
		for(int v:g[i]) printf("%d ",v-1);
		puts("");
	}

	return 0;
}