#include<bits/stdc++.h>
using namespace std;
const int N = 1505;
set<int> e[N];
vector<int>a;
int siz[N], tot, root, del[N] = { 0 }, f[N], s[N];
int dfs(int u, int fa) {
	int ans = 0;
	f[u] = fa;
	for (auto& v : e[u]) {
		if (del[v] || v == fa)continue;
		s[u] = v;
		ans |= dfs(v, u);
	}
	if (ans == 0 && e[u].size() <= 2) {
		a.push_back(u);
		return 1;
	}
	return 0;
}
void solve() {
	int n;
	cin >> n;
	for (int i = 1; i < n; i++) {
		int u, v;
		cin >> u >> v;
		e[u].insert(v);
		e[v].insert(u);
	}
	tot = n;
	vector<vector<int>> ans;
	vector<int> b;
	while (tot) {
		b.clear();
		for (int i = 1; i <= n; i++)if (!del[i]){ 
			root = i;
			a.clear();
			dfs(root, 0);
			if (a.size() > b.size())b = a;
		}
		for (auto& u : b) {
			del[u] = 1;
			tot--;
			if (e[u].size() == 1) {
				int v = *e[u].begin();
				e[v].erase(u);
			}
			else if (e[u].size() == 2) {
				int v1 = *e[u].begin();
				int v2 = *e[u].rbegin();
				e[v1].insert(v2), e[v2].insert(v1);
				e[v1].erase(u), e[v2].erase(u);
			}
		}
		ans.push_back(b);
	}
	cout << ans.size() << '\n';
	for (auto& p : ans) {
		cout << p.size() << ' ';
		for (auto& v : p)cout << v << ' ';
		cout << '\n';
	}
}
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	//int t;
	//cin >> t;
	//while (t--)
	solve();

	return 0;
}