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