#include<bits/stdc++.h>
using namespace std;
const int N=5e5+5;
int n,m;
vector < pair<int,int> > G[N];

int dfn[N],low[N],id;
bool vis[N],cut[N];
void tarjan(int u,int fa){
	dfn[u]=low[u]=++id;
	vis[u]=1;
	for(pair<int,int> e: G[u]){
		int v=e.first,num=e.second;
		if(num==fa) continue;
		if(!dfn[v]){
			tarjan(v,num);
			low[u]=min(low[u],low[v]);
			if(low[v]>dfn[u]) cut[num]=1;
		}
		else if(vis[v]) low[u]=min(low[u],dfn[v]);
	}
}

int aid;
vector <int> ANS[N];
void dfs(int u){
	if(vis[u]) return ;
	vis[u]=1;
	ANS[aid].push_back(u);
	for(pair<int,int> e: G[u]){
		int v=e.first,num=e.second;
		if(cut[num]) continue;
		dfs(v);
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		int u,v; cin>>u>>v; u++,v++;
		G[u].push_back({v,i});
		G[v].push_back({u,i});
	}
	for(int i=1;i<=n;i++)
		if(!dfn[i]) tarjan(i,0);
	
	memset(vis,0,sizeof(vis));
	for(int i=1;i<=n;i++){
		if(vis[i]) continue;
		aid++;
		dfs(i);
	}
	cout<<aid<<'\n';
	for(int i=1;i<=aid;i++){
		cout<<ANS[i].size()<<" ";
		for(int x: ANS[i]) cout<<x-1<<" ";
		cout<<'\n';
	}
}