10. Check Prime / Advanced Loops

using System;
class checkPrime
{
    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        double actualNumber = n;
        double counter = 0;
        if (n < 2)
        {
            Console.WriteLine("Not prime"); return;
        }
        for (int i = 0; i < n; i++)
        {
            if (n % actualNumber == 0)
            {
                counter += 1;
            }
            else
            {
                counter += 0;
            }
            actualNumber--;
        }
        if (counter > 2)
        {
            Console.WriteLine("Not prime");
        }
        else
        {
            Console.WriteLine("Prime");
        }
    }
}