#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);
    }
}

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);
    }
    for(int i=1;i<=n;++i)
    {
        if(e[i].size() == 1)
        {
            rt=i;
        }
    }
    dfs(rt,0);
    while(tot<n)
    {
        tmp.clear();
        dfs2(rt);
        for(int x:tmp)
        {
            if(x==rt)
            {
                if(e[x].size()==0) rt=0;
                else rt=*e[x].begin();
            }
            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();
    }
    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;
}