using System;
using System.Linq;

public class Test
{
	public static void Main()
	{
		Console.WriteLine(ReplaceEveryNInEveryWord("1234567 12345\n1234", 3, '#', " \n;"));
        Console.ReadLine();
	}
	
	        private static string ReplaceEveryNInEveryWord (string inputString, short n, char replaceToWhat, string separators)
        {
            char[] temp = inputString.ToArray();
            byte countToN = new byte();
            for (int i = 0; i < temp.Length; i++)
            {
                countToN++;
                if (separators.Contains(temp[i])) countToN = 0;
                else if (countToN % n == 0) temp[i] = replaceToWhat;
            }

            return new string(temp);
        }
}