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


#define F(i, a, b) for (int i = (a), iee = (b); i <= iee; i++)
#define R(i, a, b) for (int i = (a), iee = (b); i >= iee; i--)

const int N = 510;
int n;

int G[N][N];
int tag[N], vis[N], del[N];
vector<int> tmp;
vector<vector<int>> res;

void dfs(int x, int fa) {
    vis[x] = 1;
    int deg = 0;
    bool ok = true;
    F(i, 1, n) if (!del[i] && G[x][i] && !vis[i]) {
        deg++, dfs(i, x);
        if (tag[i]) ok = false;
    }
    if (ok && deg <= 2) tmp.push_back(x), tag[x] = 1;
}

bool solve() {
    int rt = 0;
    F(i, 1, n) if (!del[i]) rt = i;
    if (!rt) return 0;
    
    F(i, 1, n) tag[i] = vis[i] = 0;
    tmp.clear();
    dfs(rt, 0);
    assert(tmp.size());

    for (int v: tmp) {
        vector<int> nei;
        F(i, 1, n) if (G[v][i] && !del[i]) nei.push_back(i);
        for (int x: nei) for (int y: nei) if (x != y) G[x][y] = 1;
    }
    for (int v: tmp) del[v] = 1;
    res.push_back(tmp);
    return 1;
}
int main() {
    cin.tie(0)->sync_with_stdio(0), cout.tie(0);
    cin >> n;
    F(i, 2, n) { int x, y; cin >> x >> y; G[x][y] = G[y][x] = 1; }
    
    while (solve());

    cout << res.size() << "\n";
    for (auto t: res) {
        cout << t.size() << " ";
        for (int x: t) cout << x << " ";
        cout << "\n";
    }
}