#include<bits/stdc++.h>

#define vc vector
#define db double
#define fi first
#define se second
#define ll long long
#define mk make_pair
#define pb push_back
#define RI register int
#define PI pair<int,int>
#define ull unsigned long long
#define err cerr << "   -_-   " << endl
#define debug cerr << " ------------------- " << endl

#define input(x) freopen(#x".in","r",stdin)
#define output(x) freopen(#x".out","w",stdout)

#define NO puts("No")
#define YES puts("Yes")

//#define OccDreamer
//#define int long long

using namespace std;

namespace IO{
	inline int read(){
		int X=0, W=0; char ch=getchar();
		while(!isdigit(ch)) W|=ch=='-', ch=getchar();
		while(isdigit(ch)) X=(X<<1)+(X<<3)+(ch^48), ch=getchar();
		return W?-X:X;
	}
	inline void write(int x){
		if(x<0) x=-x, putchar('-');
		if(x>9) write(x/10);
		putchar(x%10+'0');
	}
	inline void sprint(int x){write(x), putchar(32);}
	inline void eprint(int x){write(x), putchar(10);}
}using namespace IO;

const int MAXN = 2e6+5;

int colcnt, Max[MAXN];
int cntt[MAXN], fa[MAXN], de[MAXN], tt;
int n, m, tot, bel[MAXN], dfn[MAXN], low[MAXN];
int head[MAXN], ne[MAXN<<1], to[MAXN<<1], topf, stk[MAXN], cnt=1;

bool vis[MAXN], del[MAXN], oop[MAXN];

vc<int> G[MAXN], las[MAXN], ans[MAXN], node;

mt19937_64 rnd(time(0));

map<ull,int> P;

PI tr[MAXN];

ull Q[MAXN];

int mark[MAXN];

inline void add(int x, int y){++cnt;to[cnt]=y;ne[cnt]=head[x];head[x]=cnt;}

inline void tarjan(int x, int fid){
	low[x]=dfn[x]=++tot; stk[++topf]=x;
	for(int i=head[x];i;i=ne[i]){
		if(dfn[to[i]]){
			if(i!=(fid^1)) low[x]=min(low[x],dfn[to[i]]);	
		}
		else tarjan(to[i],i), low[x]=min(low[x],low[to[i]]);
	}
	if(dfn[x]==low[x]){
		++colcnt; stk[topf+1]=0;
		while(stk[topf+1]!=x){
			int t=stk[topf];
			bel[t]=colcnt; --topf;
		}
	}
	return ;
}

inline void dfs(int x, int f, int fid){
	vis[x]=1; de[x]=de[f]+1; fa[x]=f;
	for(int i=head[x];i;i=ne[i]){
		if(bel[to[i]]!=bel[x] || (i==(fid^1))) continue;
		if(vis[to[i]]){
			if(de[to[i]]<de[x]) tr[++tt]=mk(x,to[i]);
			continue;
		}
		dfs(to[i],x,i); G[x].pb(to[i]);
	}
	return ;
}

inline void dfs2(int x, int f){
	node.pb(x);
	for(auto i:G[x]){
		dfs2(i,x);
		cntt[x]+=cntt[i];
		Q[x]^=Q[i]; mark[x]+=mark[i];
	}
	return ;
}

inline void dfs3(int x, int f){
	if(cntt[x]==1) del[x]=1, oop[x]=1;
	if(cntt[x]>=2 && P[Q[x]]){
		del[x]=del[P[Q[x]]]=1;
		Max[P[Q[x]]]=x;
	}
	if(cntt[x]>=2 && !P[Q[x]]) P[Q[x]]=x;
	for(auto i:G[x]) dfs3(i,x);
	return ;
}	

inline void dfs4(int x, int f){
	mark[x]=mark[f]+(del[x]==1);
	for(auto i:G[x]) dfs4(i,x);
	return ;	
}

bool inans[MAXN];

inline void find(int x, int b){
	ans[b].pb(x); inans[x]=1;
	for(auto i:las[x]) if(!inans[i]) find(i,b);
	return ;	
}

signed main(){
	n=read(), m=read();
	for(int i=1;i<=m;++i){
		int x, y;
		x=read()+1, y=read()+1;
		if(x==y) continue;
		add(x,y), add(y,x);	
	}
	for(int i=1;i<=n;++i) if(!dfn[i]) tarjan(i,0);
	for(int i=1;i<=n;++i){
		if(!vis[i]){
			tt=0; dfs(i,0,0); ull vo;
			for(int j=1;j<=tt;++j){
				int x=tr[j].fi, y=tr[j].se;
				if(de[x]>de[y]) swap(x,y);
				cntt[x]--; cntt[y]++; vo=rnd();
				Q[x]^=vo; Q[y]^=vo; 
			}
			node.clear(); dfs2(i,0); 
			P.clear(); dfs3(i,0); del[i]=1; dfs4(i,0);
			for(auto j:node) if(del[j]==0 && fa[j]) las[fa[j]].pb(j), las[j].pb(fa[j]);
			for(auto j:node) if(Max[j]) las[Max[j]].pb(fa[j]), las[fa[j]].pb(Max[j]);
			for(int j=1;j<=tt;++j){
				int x=tr[j].fi, y=tr[j].se;
				if(de[x]>de[y]) swap(x,y);
				if(mark[y]-mark[x]) continue;
				las[x].pb(y), las[y].pb(x);
			}
		}
	}
	int ss=0;
	for(int i=1;i<=n;++i){
		if(inans[i]) continue;
		++ss; find(i,ss);	sort(ans[ss].begin(),ans[ss].end());
	}
	eprint(ss);
	for(int i=1;i<=ss;++i){
		sprint(ans[i].size());
		for(auto j:ans[i]) sprint(j-1);
		putchar(10);
	}
	return 0;
}