#include<iostream>
#include<cassert>
#include<vector>
#include<cstdio>
#include<set>
using namespace std;
#define For(i,l,r) for(int i=l;i<=r;i++)
#define FOR(i,r,l) for(int i=r;i>=l;i--)
#define ll long long
#define N 505
int n;set<int>E[N];bool vis[N];bool vis0[N];
int cnt,tot;vector<int>ans[11];
ll get()
{
	ll x;
	scanf("%lld",&x);
	return x;
}
void dfs(int u,int f)
{
	vis0[u]=1;
	if(!vis[f]&&E[u].size()<=2)vis[u]=1,ans[cnt].push_back(u);
	for(auto v:E[u])if(v!=f)dfs(v,u);
}
void era(int u)
{
	if(E[u].size()==1){for(auto v:E[u])E[v].erase(u);}
	else
	{
		int pre=0;
		for(auto v:E[u])
		{
			if(pre)E[v].insert(pre),E[pre].insert(v);
			pre=v;
			E[v].erase(u);
		}
	}
}
int main()
{
	n=get();
	For(i,1,n-1)
	{
		int u=get(),v=get();
		E[u].insert(v),E[v].insert(u);
	}
	For(i,1,10)
	{
		For(j,1,n)vis0[j]=0;
		cnt=i;
		For(j,1,n)if(!vis[j]&&!vis0[j])
		{
			dfs(j,0);
		}
		for(auto j:ans[i])era(j),tot++;
		if(i==10)assert(tot==n);
		if(tot==n)break;
	}
	cout<<cnt<<'\n';
	For(i,1,cnt)
	{
		cout<<ans[i].size()<<' ';
		for(auto j:ans[i])cout<<j<<' ';
		cout<<'\n';
	}
	return 0;
}