#include <bits/stdc++.h>

using i64 = long long;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int n;
    std::cin >> n;
    
    std::vector<std::vector<int>> adj(n);
    for (int i = 1; i < n; i++) {
        int u, v;
        std::cin >> u >> v;
        u--, v--;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    
    int cnt = n;
    std::vector<bool> vis(n);
    std::vector<std::vector<int>> ans;
    while (cnt > 0) {
        int r = 0;
        while (vis[r]) {
            r++;
        }
        std::vector<int> v;
        auto dfs = [&](auto self, int x, int p) -> bool {
            bool ok = adj[x].size() <= 2;
            for (auto y : adj[x]) {
                if (y == p) {
                    continue;
                }
                ok &= !self(self, y, x);
            }
            if (ok) {
                v.push_back(x);
            }
            return ok;
        };
        dfs(dfs, r, -1);
        ans.push_back(v);
        for (auto x : v) {
            cnt--;
            vis[x] = true;
            for (auto y : adj[x]) {
                adj[y].erase(std::find(adj[y].begin(), adj[y].end(), x));
            }
            if (adj[x].size() == 2) {
                int a = adj[x][0];
                int b = adj[x][1];
                adj[a].push_back(b);
                adj[b].push_back(a);
            }
        }
    }
    
    std::cout << ans.size() << "\n";
    for (auto v : ans) {
        std::cout << v.size();
        for (auto x : v) {
            std::cout << " " << x + 1;
        }
        std::cout << "\n";
    }
    
    return 0;
}