Problem 16.** Bit Exchange (Advanced)

namespace _16.BitExchange_Advanced_
{
    using System;
    class Program
    {
        static void Main()
        {
            Console.Write("Enter n : ");
            long n = long.Parse(Console.ReadLine());
            Console.Write("Enter p : ");
            sbyte p = sbyte.Parse(Console.ReadLine());
            Console.Write("Enter q : ");
            sbyte q = sbyte.Parse(Console.ReadLine());
            Console.Write("Enter k : ");
            sbyte k = sbyte.Parse(Console.ReadLine());

            if ((p + k > 32) || (q + k > 32) || p < 0 || q < 0)
            {
                Console.WriteLine("Out of range!");
                return;
            }
            if (Math.Min(p, q) + k >= Math.Max(p, q))
            {
                Console.WriteLine("Overlapping!");
                return;
            }
            int mask1 = 0;
            for (int i = 0; i < k; i++)
            {
                mask1 = mask1 * 2 + 1;
            }
            int mask2 = mask1;
            mask1 = mask1 << p;
            mask2 = mask2 << q;
            long gettingFirstBits = ((Math.Min(p, q) == p ? mask1 : mask2) & n) << Math.Max(p, q) - Math.Min(p, q);
            long gettingSecondBits = ((Math.Max(p, q) == p ? mask1 : mask2) & n) >> Math.Max(p, q) - Math.Min(p, q);

            long mask3 = ~mask1 & n;
            long mask4 = ~mask2 & n;
            n = (gettingFirstBits | gettingSecondBits) | (mask3 & mask4);
            Console.WriteLine(n);
        }
    }
}