#include <bits/stdc++.h>

const int N = 555;

int n;
std::list<int> E[N];
bool del[N];
bool now_del[N];
bool vis[N];

void dye(int x,int c) {
    vis[x]=true;
    if (c) {
        now_del[x]=true;
    }
    for (auto y:E[x]) {
        if (vis[y]) continue;
        if (E[y].size()>2) {
            dye(y,0);
        } else {
            if (E[x].size()>2) {
                dye(y,1);
            } else {
                dye(y,1-c);
            }
        }
    }
}
std::vector<int> res[15];

void show() {
    for (int x=1;x<=n;x++) {
        if (del[x]) continue;
        std::printf("[%d]:",x);
        for (auto y:E[x]) {
            std::printf("%d ",y);
        }
        std::cout<<std::endl;
    }

}

int main() {
    std::cin>>n;
    for (int i=1;i<=n-1;i++) {
        int x,y;
        std::cin>>x>>y;
        E[x].push_back(y);
        E[y].push_back(x);
    }
    int m=0;
    int now_n=n;
    while (now_n>0) {
        // show();
        m++;
        std::fill_n(vis+1,n,false);
        int st=0;
        for (int i=1;i<=n;i++) {
            if (del[i]) continue;
            if (E[i].size()<=1) {
                st=i;
                break;
            }
        }
        dye(st,1);
        for (int i=1;i<=n;i++) {
            if (now_del[i]) {
                res[m].push_back(i);
                if (E[i].size()==1) {
                    auto x=E[i].front();
                    E[x].remove(i);
                } else if (E[i].size()==2) {
                    auto x=E[i].front();
                    auto y=E[i].back();
                    E[x].remove(i);
                    E[y].remove(i);
                    E[x].push_back(y);
                    E[y].push_back(x);
                }
                now_del[i]=false;
                del[i]=true;
                E[i].clear();
            }
        }
        now_n-=res[m].size();
    }
    std::cout<<m<<std::endl;
    for (int i=1;i<=m;i++) {
        std::cout<<res[i].size();
        for (auto x:res[i]) {
            std::cout<<" "<<x;
        }
        std::cout<<std::endl;
    }
}