As you know, Bob's brother lives in Flatland. In Flatland there are n cities, connected by n - 1 two-way roads. The cities are numbered from 1 to n. You can get from one city to another moving along the roads.

The «Two Paths» company, where Bob's brother works, has won a tender to repair two paths in Flatland. A path is a sequence of different cities, connected sequentially by roads. The company is allowed to choose by itself the paths to repair. The only condition they have to meet is that the two paths shouldn't cross (i.e. shouldn't have common cities).

It is known that the profit, the «Two Paths» company will get, equals the product of the lengths of the two paths. Let's consider the length of each road equals 1, and the length of a path equals the amount of roads in it. Find the maximum possible profit for the company.

Input

The first line contains an integer n (2 ≤ n ≤ 200), where n is the amount of cities in the country. The following n - 1 lines contain the information about the roads. Each line contains a pair of numbers of the cities, connected by the road ai, bi (1 ≤ ai, bi ≤ n).

Output

Output the maximum possible profit.

Examples

Input

4
1 2
2 3
3 4


Output

1


Input

7
1 2
1 3
1 4
1 5
1 6
1 7


Output

0


Input

6
1 2
2 3
2 4
5 4
6 4


Output

4
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Random;
import java.util.Scanner;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;
import java.lang.Long;
import java.math.BigDecimal;
import java.math.BigInteger;

/**
 * Problem statement: http://codeforces.com/problemset/problem/431/D
 * 
 * @author thepham
 * 
 */

public class D_Round_14_Div2 {
	static long Mod = 1000000007;
	static int num = 0;
	static int[] index, low;

	public static void main(String[] args) throws FileNotFoundException {
		// PrintWriter out = new PrintWriter(new FileOutputStream(new File(
		// "output.txt")));
		PrintWriter out = new PrintWriter(System.out);
		Scanner in = new Scanner();

		int n = in.nextInt();
		Point[] data = new Point[n - 1];
		ArrayList<Integer>[] map = new ArrayList[n];
		for (int i = 0; i < n; i++) {
			map[i] = new ArrayList();
		}
		for (int i = 0; i < n - 1; i++) {
			int a = in.nextInt() - 1;
			int b = in.nextInt() - 1;
			data[i] = new Point(a, b);
			map[a].add(i);
			map[b].add(i);
		}
		int result = 0;
		for (int i = 0; i < n - 1; i++) {
			int a = data[i].x;
			int b = data[i].y;
			int x = getMax(a, n, i, map, data);
			int y = getMax(b, n, i, map, data);
			result = Math.max(x * y, result);
		}
		out.println(result);

		out.close();
	}

	public static int getMax(int a, int n, int i, ArrayList<Integer>[] map,
			Point[] data) {
		int[] check = new int[n];
		LinkedList<Integer> q = new LinkedList();
		check[a] = 0;
		q.add(a);
		int max = a;

		while (!q.isEmpty()) {
			int node = q.removeFirst();
			for (int j : map[node]) {
				if (j != i) {
					int nxt = data[j].x == node ? data[j].y : data[j].x;
					if (check[nxt] == 0 && nxt != a) {
						check[nxt] = check[node] + 1;
						if (check[nxt] > check[max]) {
							max = nxt;
						}
						q.add(nxt);
					}
				}
			}
		}
		q.add(max);
		check = new int[n];
		int other = max;
		while (!q.isEmpty()) {
			int node = q.removeFirst();
			for (int j : map[node]) {
				if (j != i) {
					int nxt = data[j].x == node ? data[j].y : data[j].x;
					if (check[nxt] == 0 && nxt != max) {
						check[nxt] = check[node] + 1;
						if (check[nxt] > check[other]) {
							other = nxt;
						}
						q.add(nxt);
					}
				}
			}
		}
		return check[other];
	}

	public static int get(int node, int[] union) {
		if (node != union[node]) {
			return union[node] = get(union[node], union);
		}
		return node;
	}

	public static int[] buildKMP(String val) {
		int[] data = new int[val.length() + 1];
		int i = 0;
		int j = -1;
		data[0] = -1;
		while (i < val.length()) {
			while (j >= 0 && val.charAt(i) != val.charAt(j)) {
				j = data[j];
			}
			i++;
			j++;

			data[i] = j;
			// System.out.println(val + " " + i + " " + data[i]);
		}
		return data;
	}

	static int find(int index, int[] u) {
		if (u[index] != index) {
			return u[index] = find(u[index], u);
		}
		return index;
	}

	static int crossProduct(Point a, Point b) {
		return a.x * b.y + a.y * b.x;
	}

	static long squareDist(Point a) {
		long x = a.x;
		long y = a.y;
		return x * x + y * y;
	}

	static Point minus(Point a, Point b) {
		return new Point(a.x - b.x, a.y - b.y);
	}

	public static boolean nextPer(int[] data) {
		int i = data.length - 1;
		while (i > 0 && data[i] < data[i - 1]) {
			i--;
		}
		if (i == 0) {
			return false;
		}
		int j = data.length - 1;
		while (data[j] < data[i - 1]) {
			j--;
		}
		int temp = data[i - 1];
		data[i - 1] = data[j];
		data[j] = temp;
		Arrays.sort(data, i, data.length);
		return true;
	}

	static class Point {
		int x, y;

		public Point(int x, int y) {
			super();
			this.x = x;
			this.y = y;
		}

		public String toString() {
			return "{" + x + " " + y + "}";
		}

		@Override
		public int hashCode() {
			final int prime = 31;
			int result = 1;
			result = prime * result + x;
			result = prime * result + y;
			return result;
		}

		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (obj == null)
				return false;
			if (getClass() != obj.getClass())
				return false;
			Point other = (Point) obj;
			if (x != other.x)
				return false;
			if (y != other.y)
				return false;
			return true;
		}

	}

	static long gcd(long a, long b) {
		if (b == 0) {
			return a;
		}
		return gcd(b, a % b);
	}

	public static class FT {

		int[] data;

		FT(int n) {
			data = new int[n];
		}

		public void update(int index, int value) {
			while (index < data.length) {
				data[index] += value;
				index += (index & (-index));
			}
		}

		public int get(int index) {
			int result = 0;
			while (index > 0) {
				result += data[index];
				index -= (index & (-index));
			}
			return result;

		}
	}

	static class Scanner {

		BufferedReader br;
		StringTokenizer st;

		public Scanner() throws FileNotFoundException {
			// System.setOut(new PrintStream(new
			// BufferedOutputStream(System.out), true));
			br = new BufferedReader(new InputStreamReader(System.in));
			// br = new BufferedReader(new InputStreamReader(new
			// FileInputStream(
			// new File("input.txt"))));
		}

		public String next() {

			while (st == null || !st.hasMoreTokens()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (Exception e) {
					throw new RuntimeException();
				}
			}
			return st.nextToken();
		}

		public long nextLong() {
			return Long.parseLong(next());
		}

		public int nextInt() {
			return Integer.parseInt(next());
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public String nextLine() {
			st = null;
			try {
				return br.readLine();
			} catch (Exception e) {
				throw new RuntimeException();
			}
		}

		public boolean endLine() {
			try {
				String next = br.readLine();
				while (next != null && next.trim().isEmpty()) {
					next = br.readLine();
				}
				if (next == null) {
					return true;
				}
				st = new StringTokenizer(next);
				return st.hasMoreTokens();
			} catch (Exception e) {
				throw new RuntimeException();
			}
		}
	}

}
