#include<bits/stdc++.h>
using namespace std;

const int N=500+10;
int n,f[N],tot,rt;
bool del[N];
set<int>e[N];
vector<int>tmp;
vector<vector<int>>ans;

void dfs(int x,int fa)
{
	f[x]=fa;
	if(fa) e[x].erase(fa);
	for(int y:e[x]) dfs(y,x);
}

void dfs2(int x)
{
	if(e[x].size()==0)
	{
		del[x]=1,tmp.push_back(x);
	}
	for(int y:e[x]) dfs2(y);
	if(e[x].size()==1&&!del[*e[x].begin()])
	{
		del[x]=1,tmp.push_back(x);
	}
	else if(x==rt&&e[x].size()==2&&!del[*e[x].begin()]&&!del[*++e[x].begin()])
	{
		del[x]=1,tmp.push_back(x);
	}
}

int main()
{
	// freopen("1.in","r",stdin);
	scanf("%d",&n);
	for(int i=1;i<n;++i)
	{
		int x,y; scanf("%d%d",&x,&y);
		e[x].insert(y),e[y].insert(x);
	}
	srand(time(0));
	for(int i=1;i<=n;++i)
	{
		if(e[i].size()>1)
		{
			rt=i;
		}
	}
	dfs(rt,0);
	while(tot<n)
	{
		tmp.clear();
		// printf("-begin\n");
		dfs2(rt);
		// printf("-end\n");
		for(int x:tmp)
		{
			if(x==rt)
			{
				if(e[x].size()==0) rt=0;
				else if(e[x].size()==1) rt=*e[x].begin();
				else
				{
					int son1=*e[x].begin(),son2=*++e[x].begin();
					f[son2]=0,f[son1]=son2,e[son2].insert(son1),rt=son2;
					// f[son1]=0,f[son2]=son1,e[son1].insert(son2),rt=son1;
				}
				continue;
			}
			int fa=f[x],son=e[x].empty()?0:(*e[x].begin());
			if(fa)
			{
				e[fa].erase(x);
				if(son) e[fa].insert(son);
			}
			if(son) f[son]=fa;
		}
		ans.push_back(tmp);
		tot+=tmp.size();
		// printf("tot = %d\n",tot);
	}
	if(ans.size()>10) while(1);
	printf("%d\n",ans.size());
	for(vector<int>now:ans)
	{
		printf("%d ",now.size());
		for(int x:now) printf("%d ",x);
		puts("");
	}
	return 0;
}