SummertimeForProgrammers

using System;
using System.Text;
class SummertimeForProgrammers
{
    static void Main()
    {
        byte n = byte.Parse(Console.ReadLine());
        string topSpace = new string(' ', n / 2);
        string top = new string('*', n + 1);
        StringBuilder sb = new StringBuilder(top);
        Console.WriteLine(topSpace + top);
        sb.Replace('*', ' ', 1, n - 1);
        sb.Insert(0, topSpace);
        for (int i = 0; i < n / 2 + 1; i++)
        {
            Console.WriteLine(sb);
        }
        while(sb.Length < 2 * n - 1)
        {
            sb.Remove(0, 1);
            sb.Insert(n / 2, " ", 2);
            Console.WriteLine(sb);
        }
        sb.Clear();
        sb.Append("**");
        sb.Insert(1, ".", 2 * n - 2);
        for (int i = 0; i < n; i++)
        {
            Console.WriteLine(sb);
        }
        sb.Replace('.', '@');
        for (int i = 0; i < n; i++)
        {
            Console.WriteLine(sb);
        }
        string bottom = new string('*', 2 * n);
        Console.WriteLine(bottom);
    }
}