Числовая последовательность 5n/n! - C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace ConsoleApplication6
{
    class Program
    {
        static void Main(string[] args)
        {
            double c, s, max, k, n;
            do { n = double.Parse(Console.ReadLine()); }
            while (n <= 0); max = 0; k = 0; if (n > 0)
            {
                max = 5; k = 1; c = 1;
                for (int i = 0; i < n; ++i)
                {
                    c *= i; s = Math.Exp(Math.Log(5, Math.E) * i) / c;
                    if (s > max) { max = s; k = i; }
                }
            }
            Console.WriteLine("max = {0}, k = {1}", max, k);
            Console.ReadLine();
        }
    }
}