internal class BookReturn
 {
     public DateTime ReturnedOn { get; set; }
     public DateTime DueOn { get; set; }

     public BookReturn(string returnedOn, string dueOn)
     {
         var returnedOnValues = returnedOn.Split(" ").Select(ch => int.Parse(ch)).ToArray();
         var dueOnValues = dueOn.Split(" ").Select(ch => int.Parse(ch)).ToArray();

         ReturnedOn = new DateTime(returnedOnValues[2], returnedOnValues[1], returnedOnValues[0]);
         DueOn = new DateTime(dueOnValues[2], dueOnValues[1], dueOnValues[0]);

     }

     public BookReturn(int d1, int m1, int y1, int d2, int m2, int y2)
     {
         ReturnedOn = new DateTime(y1, m1, d1);
         DueOn = new DateTime(y2, m2, d2);
     }

     public bool IsLateWithinSameYear => ReturnedOn.Year == DueOn.Year;

     public bool IsLateWithinSameMonth => IsLateWithinSameYear && ReturnedOn.Month == DueOn.Month;

     public bool IsLateMoreThanAYear => ReturnedOn.Year != DueOn.Year;

     public bool IsReturnedOnTime => ReturnedOn.Date <= DueOn.Date;

     public int LateFee => Math.Abs(CalculateFee());

     private int CalculateFee()
     {
         if (IsReturnedOnTime)
             return 0;

         if (IsLateWithinSameMonth)
         {
             return 15 * (DueOn.Date - ReturnedOn.Date).Days;
         }

         if (IsLateWithinSameYear)
         {
             return 500 * (DueOn.Month - ReturnedOn.Month);
         }

         if (IsLateMoreThanAYear)
         {
             return 10000;
         }

         return 0;
     }
 }