Loops N! / K!

using System;
class DividesTwoFactorials
{
    static void Main()
    {
        Console.Write("write N: ");
        int N = int.Parse(Console.ReadLine());
        Console.Write("write K: ");
        int K = int.Parse(Console.ReadLine());
        Factorial(N, K);
        Console.WriteLine("N! / K! = {0}", Factorial(N, K));
    }

    static long Factorial(int N, int K)
    {
        long factorial = 1;
        for (int i = K + 1; i <= N; i++)
        {
            factorial = factorial * i;
        }
        return factorial;
    }
}