Trapezoid

using System;

class Program
{
    static void Main()
    {
        int N = int.Parse(Console.ReadLine());
        int bottom = N * 2;
        int height = N + 1;

        int leftDots = 0;
        int rightDots = 0;
        string row = null;

        // print top row
        row = new string('.', N) + new string('*', N);
        Console.WriteLine(row);

        for (int i = 0; i < height - 2; i++)
        {
            leftDots = N - i - 1;
            rightDots = N - 1 + i;
            row = new string('.', leftDots);
            row += "*";
            row += new string('.', rightDots);
            row += "*";
            Console.WriteLine(row);
        }

        // print bottom row
        row = new string('*', bottom);
        Console.WriteLine(row);
    }
}