def pascal(c: Int, r: Int): Int = {
    if (c == 0 || c == r) 1 else (pascal(c - 1, r - 1) + pascal(c, r - 1))
  }

  def balance(chars: List[Char]): Boolean = {
    def balance_helper(chars: List[Char], total: Int): Boolean = {
      if (total < 0) {
        return false
      }

      chars match {
        case List() => (total == 0)
        case '(' :: rest => balance_helper(rest, total + 1)
        case ')' :: rest => balance_helper(rest, total - 1)
        case _ :: rest => balance_helper(rest, total)
      }
    }
    return balance_helper(chars, 0)
  }