class Program
    {
        static void Main(string[] args)
        {
            string content = "caocao is a great man in chinese history";
            Console.WriteLine(content.Filter());
        }
    }
    public static class StringExtensions
    {
        public static string Filter(this string str)
        {
            string[] dirtyWords = new String[] { "kao", "fuck", "cao" };
            foreach (string dirtyWord in dirtyWords)
            {
                str = str.Replace(dirtyWord, "#blocked word#");
            }
            return str;
        }
    }