C# ters üçgen sorusu

using System;

public class TersUcgen {

    public static void Main(String[] args) {

        Console.Write("Üçgen boyutu: ");
        int a = int.Parse(Console.ReadLine());
        Console.WriteLine("");
        int b = a*2;
        while(b>=1) {
            if((b%2)==1) {
                int c = a-2;
                while(c>=b/2) {
                    Console.Write(" ");
                    c--;
                }
                c = 1;
                while(c<=b) {
                    if((c==1 || c==b) || b==(a*2)-1) {
                        Console.Write("*");
                    }
                    else {
                        Console.Write(" ");
                    }
                    c++;
                }
                Console.WriteLine("");
            }
            b--;
        }
    }
}