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.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
public class D14 
{
    static class Scanner
    {
        BufferedReader br;
        StringTokenizer tk=new StringTokenizer("");
        public Scanner(InputStream is) 
        {
            br=new BufferedReader(new InputStreamReader(is));
        }
        public int nextInt() throws IOException
        {
            if(tk.hasMoreTokens())
                return Integer.parseInt(tk.nextToken());
            tk=new StringTokenizer(br.readLine());
            return nextInt();
        }
        public long nextLong() throws IOException
        {
            if(tk.hasMoreTokens())
                return Long.parseLong(tk.nextToken());
            tk=new StringTokenizer(br.readLine());
            return nextLong();
        }
        public String next() throws IOException
        {
            if(tk.hasMoreTokens())
                return (tk.nextToken());
            tk=new StringTokenizer(br.readLine());
            return next();
        }
        public String nextLine() throws IOException
        {
            tk=new StringTokenizer("");
            return br.readLine();
        }
        public double nextDouble() throws IOException
        {
            if(tk.hasMoreTokens())
                return Double.parseDouble(tk.nextToken());
            tk=new StringTokenizer(br.readLine());
            return nextDouble();
        }
        public char nextChar() throws IOException
        {
            if(tk.hasMoreTokens())
                return (tk.nextToken().charAt(0));
            tk=new StringTokenizer(br.readLine());
            return nextChar();
        }
        public int[] nextIntArray(int n) throws IOException
        {
            int a[]=new int[n];
            for(int i=0;i<n;i++)
                a[i]=nextInt();
            return a;
        }
        public long[] nextLongArray(int n) throws IOException
        {
            long a[]=new long[n];
            for(int i=0;i<n;i++)
                a[i]=nextLong();
            return a;
        }
        public int[] nextIntArrayOneBased(int n) throws IOException
        {
            int a[]=new int[n+1];
            for(int i=1;i<=n;i++)
                a[i]=nextInt();
            return a;
        }
        public long[] nextLongArrayOneBased(int n) throws IOException
        {
            long a[]=new long[n+1];
            for(int i=1;i<=n;i++)
                a[i]=nextLong();
            return a;
        }
    
    
    }
    
    public static void main(String args[]) throws IOException
    {
        new Thread(null, new Runnable() {
            public void run() {
                try
                {
                    solve();
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }
            }
        }, "1", 1 << 26).start();
        
    }
    static ArrayList<Integer> g[];
    static int p[];
    static void dfs(int node)
    {
        for(int nn:g[node])
        {
            if(nn!=p[node])
            {
                p[nn]=node;
                dfs(nn);
            }
        }
    }
    static int pth[];
    static int lpth(int node,int wth)
    {
        if(node==wth)
            return 0;
        int max1=0,max2=0;
        for(int nn:g[node])
        {
            if(nn==p[node])
                continue;
            int v=lpth(nn,wth);
            pth[node]=Math.max(pth[node],pth[nn]);
            if(v>max1)
            {
                max2=max1;
                max1=v;
            }
            else if(v>max2)
                max2=v;
        }
        pth[node]=Math.max(pth[node],1+max1+max2);
        return 1+max1;
    }
    static void solve() throws IOException
    {
        Scanner in=new Scanner(System.in);
        PrintWriter out=new PrintWriter(System.out);
        int n=in.nextInt();
        g=new ArrayList[n+1];
        for(int i=1;i<=n;i++)
            g[i]=new ArrayList<>();
        p=new int[n+1];
        pth=new int[n+1];
        for(int i=1;i<n;i++)
        {
            int u=in.nextInt(),v=in.nextInt();
            g[u].add(v);
            g[v].add(u);
        }
        dfs(1);
        lpth(1,0);
        int path[]=pth.clone();
        int ans=0;
        for(int i=2;i<=n;i++)
        {
            Arrays.fill(pth,0);
            lpth(1,i);
            ans=Math.max(ans,(pth[1]-1)*(path[i]-1));
        }
        out.println(ans);
        out.close();
    }

}
