#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}()); 
const ll mod=998244353;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

const int N=1010;
int q[N],f[N],vis[N],sz[N],ms[N];
int n;
VI e[N];
int find(int u) {
	int t=1;q[0]=u;f[u]=-1;
	rep(i,0,t) {
		u=q[i];
		rep(j,0,e[u].size()) {
			int v=e[u][j];
			if (!vis[v]&&v!=f[u]) f[q[t++]=v]=u;
		}
		ms[q[i]]=0;
		sz[q[i]]=1;
	}
	for (int i=t-1;i>=0;i--) {
		ms[q[i]]=max(ms[q[i]],t-sz[q[i]]);
		if (ms[q[i]]*2<=t) return q[i];
		sz[f[q[i]]]+=sz[q[i]];
		ms[f[q[i]]]=max(ms[f[q[i]]],sz[q[i]]);
	}
	return 0;
}

vector<VI> ans;
void gao(int u,int lev) {
	u=find(u);
	if (SZ(ans)<=lev) ans.pb(VI());
	ans[lev].pb(u);
	vis[u]=1;
	for (auto v:e[u]) if (!vis[v]) gao(v,lev+1);
}

int main() {
	scanf("%d",&n);
	rep(i,1,n) {
		int u,v;
		scanf("%d%d",&u,&v);
		e[u].pb(v);
		e[v].pb(u);
	}
	gao(1,0);
	printf("%d\n",SZ(ans));
	reverse(all(ans));
	for (auto x:ans) {
		printf("%d", SZ(x));
		for (auto y:x) printf(" %d",y);
		puts("");
	}
}