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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.FilterInputStream;
import java.io.BufferedInputStream;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author khokharnikunj8
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        ScanReader in = new ScanReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        D_TWO_PATH solver = new D_TWO_PATH();
        solver.solve(1, in, out);
        out.close();
    }

    static class D_TWO_PATH {
        int[][] G;
        int ans;
        int which;
        int temp;

        public int dfs(int node, int parent) {
            int max1 = 0;
            int max2 = 0;
            for (int i : G[node]) {
                if (i == parent || i == which) continue;
                int temp = dfs(i, node);
                if (max1 <= temp) {
                    max2 = max1;
                    max1 = temp;
                } else if (max2 <= temp) {
                    max2 = temp;
                }
            }
            temp = Math.max(temp, max1 + max2);
            return max1 + 1;
        }

        public void solve(int testNumber, ScanReader in, PrintWriter out) {
            int n = in.scanInt();
            int[] from = new int[n - 1];
            int[] to = new int[n - 1];
            for (int i = 0; i < n - 1; i++) {
                from[i] = in.scanInt();
                to[i] = in.scanInt();
            }
            G = CodeHash.packGraph(from, to, n);
            for (int i = 0; i < n - 1; i++) {
                int ans = 1;
                which = to[i];
                temp = 0;
                dfs(from[i], -1);
                ans *= temp;
                which = from[i];
                temp = 0;
                dfs(to[i], -1);
                ans *= temp;
                this.ans = Math.max(this.ans, ans);
            }
            out.println(ans);

        }

    }

    static class CodeHash {
        public static int[][] packGraph(int[] from, int[] to, int n) {
            int[][] g = new int[n + 1][];
            int p[] = new int[n + 1];
            for (int i : from) p[i]++;
            for (int i : to) p[i]++;
            for (int i = 0; i <= n; i++) g[i] = new int[p[i]];
            for (int i = 0; i < from.length; i++) {
                g[from[i]][--p[from[i]]] = to[i];
                g[to[i]][--p[to[i]]] = from[i];
            }
            return g;
        }

    }

    static class ScanReader {
        private byte[] buf = new byte[4 * 1024];
        private int index;
        private BufferedInputStream in;
        private int total;

        public ScanReader(InputStream inputStream) {
            in = new BufferedInputStream(inputStream);
        }

        private int scan() {
            if (index >= total) {
                index = 0;
                try {
                    total = in.read(buf);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                if (total <= 0) return -1;
            }
            return buf[index++];
        }

        public int scanInt() {
            int integer = 0;
            int n = scan();
            while (isWhiteSpace(n)) n = scan();
            int neg = 1;
            if (n == '-') {
                neg = -1;
                n = scan();
            }
            while (!isWhiteSpace(n)) {
                if (n >= '0' && n <= '9') {
                    integer *= 10;
                    integer += n - '0';
                    n = scan();
                }
            }
            return neg * integer;
        }

        private boolean isWhiteSpace(int n) {
            if (n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1) return true;
            else return false;
        }

    }
}

