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

const int N = 505;

vector<int> G[N];
int siz[N], maxs[N];
bool del[N];

vector<int> G2[N];
int f[N], id[N];

void dvd(int u, int s, int fa) {

	int ms = s + 1, root = -1;
	
	function<void(int, int)> dfs1 = [&](int u, int rt) {
		siz[u] = 1;
		maxs[u] = 0;
		for (auto v : G[u]) {
			if (del[v] || v == rt) continue ;
			dfs1(v, u);
			siz[u] += siz[v];
			maxs[u] = max(maxs[u], siz[v]);
		}
		maxs[u] = max(maxs[u], s - siz[u]);
		if (maxs[u] < ms) ms = maxs[u], root = u;
	};
	
	dfs1(u, 0);
	
	G2[fa].push_back(root);

	for (auto v : G[root]) {
		
		if (del[v]) continue ;
		
		function<void(int, int)> dfs2 = [&](int u, int rt) {
			siz[u] = 1;
			for (auto v : G[u]) {
				if (del[v] || v == rt) continue ;
				dfs2(v, u);
				siz[u] += siz[v];
			}
		};
		
		dfs2(v, u); 
	}
	
	del[root] = 1;
	for (auto v : G[root]) {
		if (!del[v]) dvd(v, siz[v], root);
	}
}

void dfs(int u) {
	if (G2[u].empty()) f[u] = 1;
	for (auto v : G2[u]) {
		dfs(v);
		f[u] = max(f[u], f[v] + 1);
	}
}

void solve() {
	int n;
	cin >> n;
	for (int i = 1; i < n; i++) {
		int u, v;
		cin >> u >> v;
		G[u].push_back(v);
		G[v].push_back(u);
	}
	
	dvd(1, n, 0);
	
	dfs(0); 
	
	for (int i = 1; i <= n; i++) id[i] = i;
	
	sort(id + 1, id + n + 1, [](int A, int B) {
		return f[A] < f[B];
	});
	
	int ans = 1;
	vector<int> vec[20];
	for (int i = 1; i <= n; i++) {
		if (i > 1 && f[id[i]] != f[id[i - 1]]) ++ans;
		vec[ans].push_back(id[i]);
	}
	
	cout << ans << '\n';
	for (int i = 1; i <= ans; i++) {
		cout << vec[i].size() << ' ';
		for (auto v : vec[i]) cout << v << ' ';
		cout << '\n';
	}
}

signed main() {
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	solve();
	return 0;
}