#include <map>
#include <set>
#include <array>
#include <cmath>
#include <deque>
#include <bitset>
#include <random>
#include <string>
#include <vector>
#include <cassert>
#include <complex>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>

using namespace std;

const int MAXN = 550;
int level[MAXN];
vector<int> G[MAXN];
int sz[MAXN];

void dfs_sz(int v, int p) {
	sz[v] = 1;
	for (int u : G[v]) {
		if (u == p || level[u] != -1)
			continue;
		dfs_sz(u, v);
		sz[v] += sz[u];
	}
}

void centroid(int v, int w) {
	dfs_sz(v, -1);
	int u = v, p = -1;
	while (true) {
		pair<int, int> u_mx(-1, -1);
		for (int nxt : G[u]) {
			if (nxt == p || level[nxt] != -1)
				continue;
			u_mx = max(u_mx, make_pair(sz[nxt], nxt));
		}
		if (2 * u_mx.first >= sz[v]) {
			p = u;
			u = u_mx.second;
		} else {
			break;
		}
	}

	level[u] = w;
	for (int nxt : G[u]) {
		if (level[nxt] == -1)
			centroid(nxt, w + 1);
	}
}


int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	int n;
	cin >> n;
	for (int i = 1; i < n; ++i) {
		int a, b;
		cin >> a >> b;
		G[a - 1].emplace_back(b - 1);
		G[b - 1].emplace_back(a - 1);
	}
	fill(level, level + n, -1);
	centroid(0, 0);
	vector<vector<int>> ans(10);
	for (int i = 0; i < n; ++i)
		ans[level[i]].emplace_back(i);
	while (ans.back().empty())
		ans.pop_back();
	cout << ans.size() << '\n';
	reverse(ans.begin(), ans.end());
	for (auto& tmp : ans) {
		cout << tmp.size() << ' ';
		for (int x : tmp)
			cout << x + 1 << ' ';
		cout << '\n';
	}
	return 0;
}