#include <cstdio>
#include <vector>

using namespace std;

const int N = 505;

int n, cen[N], siz[N], naj;
vector < int > v[N], cv;

void dfs(int x, int lst) {
	cv.push_back(x); siz[x] = 1;
	for(int y : v[x]) {
		if(y != lst && !cen[y]) {
			dfs(y, x);
			siz[x] += siz[y];
		}
	}
}

int nadi_centroid() {
	int odg = cv[0];
	for(int y : cv)
		if(siz[y] < siz[odg] && 2 * siz[y] >= (int)cv.size())
			odg = y;
	return odg;
}

void solve(int x, int raz){
	naj = max(naj, raz);
	dfs(x, x);
	x = nadi_centroid();
	cv.clear(); cen[x] = raz;
	cen[x] = raz;
	for(int y : v[x])
		if(!cen[y]) solve(y, raz + 1);
}



int main(){
	scanf("%d", &n);
	for(int i = 1;i < n;i++) {
		int x, y; scanf("%d%d", &x, &y);
		v[x].push_back(y);
		v[y].push_back(x);
	}
	solve(1, 1);
	for(int i = naj;i >= 1;i--) {
		vector < int > tko;
		for(int j = 1;j <= n;j++)
			if(cen[j] == i) tko.push_back(j);
		printf("%d ", (int)tko.size());
		for(int x : tko) printf("%d ", x);
		printf("\n");
	}
	return 0;
}