#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define maxn 505
#define put() putchar('\n')
#define Tp template<typename Ty>
#define Ts template<typename Ty,typename... Ar>
using namespace std;
inline void read(int &x){
    int f=1;x=0;char c=getchar();
    while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
    while (c>='0'&&c<='9') {x=x*10+c-'0';c=getchar();}
    x*=f;
}
namespace Debug{
	Tp void _debug(char* f,Ty t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,Ty x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	Tp ostream& operator<<(ostream& os,vector<Ty>& V){os<<"[";for(auto& vv:V) os<<vv<<",";os<<"]";return os;}
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
}using namespace Debug;
#define fi first
#define se second
#define mk make_pair
const int mod=1e9+7;
inline int power(int x,int y=mod-2) {
	int sum=1;
	while (y) {
		if (y&1) sum=sum*x%mod;
		x=x*x%mod;y>>=1;
	}
	return sum;
}
int n;
vector<int> to[maxn];
int dfn[maxn],times;
vector<int>O[105];
signed main(void){
	int i,j,x,y;
	read(n);
	for (i=1;i<n;i++) {
		read(x),read(y);
		to[x].push_back(y);
		to[y].push_back(x);
	}
	int cnt=n;
	for (j=1;j<=20&&cnt;j++) {
		for (i=1;i<=n;i++) if (!dfn[i]) {
			int nums=0,tot=0;
			for (auto y:to[i]) nums+=(dfn[y]==0),tot+=(dfn[y]==j);
//			gdb(j,i,nums,tot);
			if (nums<=1&&!tot) dfn[i]=j,O[j].push_back(i),cnt--;	
		}
//		gdb(j,cnt);
		for (i=1;i<=n;i++) if (!dfn[i]) {
			int nums=0,tot=0,tmp1=0,tmp2=0,tmp3=0;
			for (auto y:to[i]) {
				if (dfn[y]==0) {
					nums++;
					if (!tmp1) tmp1=y;
					else if (!tmp2) tmp2=y;
					else if (!tmp3) tmp3=y;
				}
				tot+=(dfn[y]==j);
			}
			if (nums==2&&!tot) {
				dfn[i]=j;O[j].push_back(i);cnt--;
				to[tmp1].push_back(tmp2);
				to[tmp2].push_back(tmp1);
			}
			else if (nums==3&&!tot) {
				dfn[i]=j;O[j].push_back(i);cnt--;
				to[tmp1].push_back(tmp3);
				to[tmp3].push_back(tmp2);
				to[tmp2].push_back(tmp1);
			}
		}
	}
	int k=j-1;
	for (printf("%d\n",k),j=1;j<=k;j++) {
		printf("%d ",O[j].size());
		for (auto x:O[j]) printf("%d ",x);put();
	}
	return 0;
}