// 那就是希望。
// 即便需要取模，也是光明。

#include <algorithm>
#include <stdio.h>
#include <vector>
typedef long long llt;
typedef unsigned uint;typedef unsigned long long ullt;
typedef bool bol;typedef char chr;typedef void voi;
typedef double dbl;
template<typename T>bol _max(T&a,T b){return(a<b)?a=b,true:false;}
template<typename T>bol _min(T&a,T b){return(b<a)?a=b,true:false;}
template<typename T>T lowbit(T n){return n&-n;}
template<typename T>T gcd(T a,T b){return b?gcd(b,a%b):a;}
template<typename T>T lcm(T a,T b){return(a!=0||b!=0)?a/gcd(a,b)*b:(T)0;}
template<typename T>T exgcd(T a,T b,T&x,T&y){if(b!=0){T ans=exgcd(b,a%b,y,x);y-=a/b*x;return ans;}else return y=0,x=1,a;}
template<typename T>T power(T base,T index,T mod)
{
    T ans=1%mod;
    while(index)
    {
        if(index&1)ans=ans*base%mod;
        base=base*base%mod,index>>=1;
    }
    return ans;
}
uint U[200005],V[200005];
std::vector<uint>Way[200005],Son[200005],T[200005];
uint S[200005],Dfn[200005],cnt,tp;
voi dfs(uint p,uint ef){
	Dfn[p]=cnt++;
	for(auto e:Way[p])if(e!=ef){
		uint t=U[e]^V[e]^p;
		if(~Dfn[t]){
			if(Dfn[t]<Dfn[p])S[t]--,S[p]++;
		}else dfs(t,e),S[p]+=S[t],Son[p].push_back(t);
	}
}
voi bfs(uint p){
	std::vector<uint>A{p},B;
	while(A.size()){
		B={A.back()},A.pop_back();
		while(B.size()){
			p=B.back(),B.pop_back(),T[tp].push_back(p);
			for(auto s:Son[p])(S[s]?B:A).push_back(s);
		}
		tp++;
	}
}
int main()
{
#ifdef MYEE
    freopen("QAQ.in","r",stdin);
    freopen("QAQ.out","w",stdout);
#endif
	uint n,m;scanf("%u%u",&n,&m);
	for(uint i=0;i<n;i++)Dfn[i]=-1;
	for(uint i=0;i<m;i++)
		scanf("%u%u",U+i,V+i),Way[U[i]].push_back(i),Way[V[i]].push_back(i);
	for(uint i=0;i<n;i++)if(!~Dfn[i])dfs(i,-1),bfs(i);
	printf("%u\n",tp);
	for(uint i=0;i<tp;i++){
		printf("%u",T[i].size());
		for(auto s:T[i])printf(" %u",s);
		putchar('\n');
	}
    return 0;
}

// 那就是希望。
// 即便需要取模，也是光明。