def balance(chars: List[Char]): Boolean = {
      def isBalanced(chars: List[Char], x: Int = 0, lastChar: Char = '#'): Boolean ={
        if (chars.isEmpty)
          if (lastChar == ')' && x == 0)
            return true
          else
            return false
        if (chars.head == '(')
          isBalanced(chars.tail, x+1, chars.head)
        else if (chars.head == ')')
          isBalanced( chars.tail, x-1, chars.head)
        else
          isBalanced(chars.tail, x, lastChar)
      }
      isBalanced(chars)
    }