//Don't ask me. I don't know. Just work. If anybody can tell me why   for (int i = k + 7; i >= 0; i--)   and why we needn't n%k - Please, tell! I don't understand.

using System;

namespace ConsoleApp32
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] vvod = Console.In.ReadLine().Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
            int n = int.Parse(vvod[0]);
            string k1 = vvod[1];
            int k = k1.Length;
            int q = 1;

            for (int i = k + 7; i >= 0; i--)
                {
                    int t;
                    t = n - i * k;
                    if (t > 0) q *= t;
                }
            Console.WriteLine(q);
        }
    }
}

Edited by author 13.01.2018 23:49

because we have more than 1x! (minimum 2) and less or exactly 9 (because we have 9 numbers 2...10 and it nevermind if we have more !...! than 9).
so we have k = 9-2 =7 (maximum)
if we use % and the number of '!' is > 10 we have wrong answer, because we have zero: x%y=0

Edited by author 19.03.2023 19:49