Problem 5. Disk

using System;

class Disk
{
    static void Main()
    {
        decimal n = int.Parse(Console.ReadLine());
        decimal r = int.Parse(Console.ReadLine());

        char[,] board = new char[(int)n,(int)n];

        int x1 = 0;
        int y1 = 0;
        for (int line = 0; line < n; line++)
        {
            for (int row = 0; row < n; row++)
            {
                double x2 = line - (double)Math.Floor(n / 2);
                double y2 = row - (double)Math.Floor(n / 2);
                double pow1 = Math.Pow((x2 - x1), 2);
                double pow2 = Math.Pow((y2 - y1), 2);
                if (pow1 + pow2 <=  (int)r * (int)r)
                {
                    board[line, row] = '*';
                }
                else
                {
                    board[line, row] = '.';
                }
            }
        }

        board[(int)n / 2, (int) n / 2] = '*';
        for (int line = 0; line < n; line++)
        {
            for (int row = 0; row < n; row++)
            {
                Console.Write(board[line, row]);
            }
            Console.WriteLine();
        }
    }
}