private static string removeStarting0(string s)
        {
            StringBuilder sb = new StringBuilder();

            bool skipFirst0s = true;
            foreach (char c in s)
            {
                if (c == '0' && skipFirst0s)
                {
                    continue;
                }
                else
                {
                    skipFirst0s = false;
                    sb.Append(c);
                }
            }

            return (sb.ToString().Length == 0) ? "0" : sb.ToString();
        }