using System;

using System.Collections.Generic;

using System.Linq;

using System.Collections.Specialized;

using System.Configuration;

using System.Data;

using System.Data.SqlClient;

using System.Globalization;

using System.Reflection;

using System.Linq.Expressions;

using System.Net;

using System.Text;

using System.Threading.Tasks;

​

using System.Diagnostics;

​

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string res = "hello(hi,mo,wo,ka)";

​

        var regex =  Regex.Match(res, "\\(([^)]+)\\)");

        var result = regex.Groups[1].Value.Replace(',','*');

        Console.WriteLine(result);

    }

}