using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(StrReplaceStar("王大頭"));

    }

    /// <summary>

        /// 字串中間替換星號隱密顯示

        /// </summary>

        /// <param name="before">原始字串</param>

        /// <returns></returns>

        public static string StrReplaceStar(string before)

        {

            string result="";

            int i = 0;

            string star = "";

            i = before.Length / 2;

            if(i==0){return before;}

            for(int j=1;j<=i;j++)

            {

              star+="*";

            }

            int flow = 0;

            if (i != 1) { flow = 1; }

            result = before.Substring(0, i - flow) + star + before.Substring(i + star.Length - flow);

            return result;

        }

}