class LeftRightMid
    {
        static void Main(string[] args)
        {
            string myString = "This is a string";
            Console.WriteLine(Left(myString, 4));
            Console.WriteLine(Right(myString, 6));
            Console.WriteLine(Mid(myString, 5, 4));
            Console.WriteLine(Mid(myString, 5));
            Console.ReadLine();
        }
        public static string Left(string param, int length)
        {
            string result = param.Substring(0, length);
            return result;
        }
        public static string Right(string param, int length)
        {
            string result = param.Substring(param.Length - length, length);
            return result;
        }
        public static string Mid(string param, int startIndex, int length)
        {
            string result = param.Substring(startIndex, length);
            return result;
        }
        public static string Mid(string param, int startIndex)
        {
            string result = param.Substring(startIndex);
            return result;
        }

    }