text: int check_brackets(char* expression)
  {
      int open = 0, close = 0;
      while (*expression)
      {
          if (*expression == '(')
          {
              open++;
          }
          if (*expression == ')')
          {
              close++;
          }
          if (close > open)
          {
              return -1;
          }
          expression++;
      }
      if (open == close)
      {
          return 0;
      }
      return -1;
  }