Мат. Методы (лб1)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace лб_1
{
    class lab1
    {
        public static double accurate(int n, double perc, double sum, int month, int amountofyears)
        {
            int k = 365;
            int fully = 365;
            for (int i = 0; i <= amountofyears; i++)
            {
                if (month == 12) month = 0;
                if (month + 1 <= 7 && month + 1 > 2)
                {
                    for (; month != 12; month++)
                    {
                        if (month / 2 == 0)
                        {
                            n += 30;
                        }
                        else n += 31;
                    }
                }
                if (month + 1 > 7)
                {
                    for (; month != 12; month++)
                    {
                        if (month / 2 == 0)
                        {
                            n += 31;
                        }
                        else n += 30;
                    }
                }
                if (month + 1 == 2)
                {
                    n += 28;
                    for (; month != 12; month++)
                    {
                        if (month <= 7)
                        {
                            if (month / 2 == 0)
                            {
                                n += 30;
                            }
                            else n += 31;
                        }
                        else
                        {
                            if (month / 2 == 0)
                            {
                                n += 31;
                            }
                            else n += 30;
                        }
                    }
                }
            }
            Console.WriteLine(n);
            double fullperc = sum * n * perc;
            //Console.WriteLine(sum + " " + perc);
            return fullperc;
        }
        public static double commacc(int n, double perc, double sum)
        {
            int k = 360;
            n = n * 365;
            double fulltime = n / k;
            double fullperc = sum * fulltime * perc;
            return fullperc;
        }
        public static double comm(int n, double perc, double sum)
        {
            int k = 360;
            n = n * 360;
            double fulltime = n / k;
            double fullperc = sum * fulltime * perc;
            return fullperc;
        }
        static void Main()
        {
            Console.WriteLine("Введите необходимую сумму:");
            double sum = Convert.ToDouble(Console.ReadLine());
            Console.WriteLine("Введите процентную ставку:");
            double perc = Convert.ToDouble(Console.ReadLine());
            Console.WriteLine("Введите дату начала:");
            string n = Console.ReadLine();
            Console.WriteLine("Введите дату конца:");
            string n2 = Console.ReadLine();

            //счет времени
            int[] nn = new int[3];
            string[] ns = n.Split('.');
            for (int i = 0; i < 2; i++)
            {

                nn[i] = Convert.ToInt32(ns[i]);
            }
            int[] nn2 = new int[3];
            string[] nss = n2.Split('.');
            for (int i = 0; i < 2; i++)
            {
                nn2[i] = Convert.ToInt32(nss[i]);
            }
            int years = nn2[2] - nn[2];
            int months;
            if (nn2[1] >= nn[1]) months = nn2[1] - nn[1];
            else months = (12 - nn[1]) + nn2[1];
            int days = 0;
            if (nn2[0] >= nn[0]) days = nn2[0] - nn[0];
            else if (nn[1] / 2 == 0 && nn[1] != 2 && nn[1] < 8) days = 30 - nn[0] + nn2[0];
            else if (nn[1] == 2) days = 28 - nn[0] + nn2[0];
            else if (nn[1] / 2 == 0 && nn[1] != 2 && nn[1] >= 8) days = 31 - nn[0] + nn2[0];
            else if (nn[1] / 2 != 0 && nn[1] != 2 && nn[1] < 8) days = 31 - nn[0] + nn2[0];
            else if (nn[1] / 2 != 0 && nn[1] != 2 && nn[1] >= 8) days = 30 - nn[0] + nn2[0];

            Console.Clear();
            Console.WriteLine("Выберите метод:\n1.Метод точных процентов\n2.Метод обыкновенных процентов\n3.Метод обыкновенных процентов с приближенным числом дней ссуды");
            int choice = Convert.ToInt32(Console.ReadLine());
            double fullsum = 0;
            double I;
            switch (choice)
            {
                case 1:
                    I = accurate(days, perc, sum, months, years);
                    fullsum = sum + I;
                    Console.WriteLine("Сумма к возврату: " + fullsum);
                    break;
                    //case 2:
                    //    I = commacc(n, perc, sum);
                    //    fullsum = sum + I;
                    //    Console.WriteLine("Сумма к возврату: " + fullsum);
                    //    break;
                    //case 3:
                    //    I = comm(n, perc, sum);
                    //    fullsum = sum + I;
                    //    Console.WriteLine("Сумма к возврату: " + fullsum);
                    //    break;
            }
            Console.ReadKey();
        }
    }
}