ATM NZEC C#

using System; class t2 { public static void Main() { double x=double.Parse(Console.ReadLine()); double y=double.Parse(Console.ReadLine()); if (x%5==0) if (x>y) if (y-x<0.5) Console.WriteLine((y-x)-0.5); else Console.WriteLine(y); } } keeps doing runtime error NZEC this is in C# thanks in advance