public static void Main(string[] args)
{
int n = int.Parse(Console.ReadLine());
double m = double.Parse(Console.ReadLine());
List <Mushroom> mushrooms = new List <Mushroom>(n);
for (int i = 0; i < n; i++)
{
try
{
mushrooms.Add(Mushroom.Parse(Console.ReadLine()));
}
catch (ArgumentException e)
{
Console.WriteLine(e.Message);
}
}
double average = Mushroom.GetAverageDiameter(mushrooms, m);
Console.WriteLine(average.ToString("F2"));
}
