#include <bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define x first
#define y second

using namespace std;

typedef long double ld;
typedef long long ll;

vector <int> g[505];
int sz[505];
vector <int> answer[15];

void dfsik(int v, int pr)
{
 	sz[v] = 1;
 	for (int u : g[v])
 		if (u != pr)
 		{
 		 	dfsik(u, v);
 		 	sz[v] += sz[u];
 		}
 	auto pos = find(g[v].begin(), g[v].end(), pr);
 	if (pos != g[v].end()) g[v].erase(pos); 
 	return;
}

void centroid(int v, int height)
{
   	int pos = -1;
   	for (int i = 0; i < (int) g[v].size(); i++)
   	{
   	 	int u = g[v][i];
   	 	if (2 * sz[u] > sz[v]) pos = i;
   	}

   	if (pos == -1)
   	{
   	 	answer[height].pb(v);
   	 	for (int u : g[v]) centroid(u, height + 1);
   	 	return;	
   	}

   	int u = g[v][pos];
   	sz[v] -= sz[u];
   	sz[u] += sz[v];
   	g[v].erase(find(g[v].begin(), g[v].end(), u));
   	g[u].pb(v);
   	centroid(u, height);
   	return;
}

int main()
{
 	//freopen("input.txt", "r", stdin);
 	//freopen("output.txt", "w", stdout);
	ios_base::sync_with_stdio(0); cin.tie(0);

	int n;
	cin >> n;
	for (int i = 1; i < n; i++)
	{
	 	int a, b;
	 	cin >> a >> b;
	 	g[a].pb(b), g[b].pb(a);
	}

	dfsik(1, -1);

	centroid(1, 0);

	int num = 0;
	while (!answer[num].empty()) num++;

	cout << num << '\n';
	for (int i = num - 1; i >= 0; i--)
	{
	 	cout << answer[i].size() << ' ';
	 	for (int v : answer[i]) cout << v << ' ';
	 	cout << '\n';
	}
	return 0;
}