#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];
vector <pair <int, int> > vert;
vector <int> indep[15];
bool dead[505];

void dfs(int v, int pr, int h)
{
	vert.pb(mp(h, v));
	for (int u : g[v])
		if (u != pr) dfs(u, v, h + 1);
	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 u, v;
	 	cin >> u >> v;
	 	g[u].pb(v), g[v].pb(u);
	}

	int ans_op = 0;
	while (ans_op < 10)
	{
		ans_op++;

		int root = 0;
		for (int i = 1; i <= n; i++)
			if (!dead[i]) {root = i; break;}
		if (root == 0)
		{
		 	ans_op--;
		 	break;
		}

		vert.clear();
		dfs(root, 0, 0);
		sort(vert.begin(), vert.end());

		for (int i = (int) vert.size() - 1; i >= 0; i--)
		{
		 	int v = vert[i].y;
		 	bool fl = true;
		 	for (int u : g[v])
		 		if (dead[u]) fl = false;
		 	if (fl && (int) g[v].size() <= 2) dead[v] = true, indep[ans_op].pb(v);	
		}

		for (int v : indep[ans_op])
		{
			for (int u : g[v])
				g[u].erase(find(g[u].begin(), g[u].end(), v));
			if ((int) g[v].size() == 2)
			{
			 	int a = g[v][0], b = g[v][1];
			 	g[a].pb(b), g[b].pb(a);
			}
		}
	}

	cout << ans_op << '\n';
	for (int i = 1; i <= ans_op; i++)
	{
	 	cout << indep[i].size() << ' ';
	 	for (int v : indep[i]) cout << v << ' ';
	 	cout << '\n';
	}
	return 0;
}