import math
class Solution(object):
    def evalRPN(self, tokens):
        """
        :type tokens: List[str]
        :rtype: int
        """
        valid_tokens = {
            '+': lambda x, y: x + y,
            '-': lambda x, y: x - y,
            '*': lambda x, y: x * y,
            '/': lambda x, y: x / y,
        }
        tmp = []

        # while len(tokens) != 1:
        blanks = 0
        count = 0
        for x in range(len(tokens)):
            # print(tokens[x])
            if tokens[x] in valid_tokens:
                operator = valid_tokens[tokens[x]]
                if len(tmp) > 1 and count == 0:
                    a = tmp.pop()
                    b = tmp.pop()
                    tokens.append(math.floor(operator(b, a)))
                    # print(tmp)
                    # print(tokens)
                    tokens[x] = None
                    count += 1
                else:
                    a = tmp.pop()
                    b = tokens.pop()
                    tokens.append(math.ceil(operator(a, b)))
                    tokens[x] = None
            else:
                tmp.append(int(tokens[x]))
                tokens[x] = None
            # print(tokens)
            # print(tmp)
        for y in tokens:
            if y is None:
                blanks += 1
                # print(blanks)
        tokens = tokens[blanks:]
        if tokens[0] < 0:
            tokens[0] *= -1
        return int(tokens[0])

obj = Solution()
# print(obj.evalRPN(["2","1","+","3","*"])) # 9
# print(obj.evalRPN(["4","13","5","/","+"])) # 6
# print(obj.evalRPN(["10","6","9","3","+","-11","*","/","*","17","+","5","+"])) # 22
# print(obj.evalRPN(["0","3","/"])) # 0
print(obj.evalRPN(["3","11","+","5","-"])) # 9
print(obj.evalRPN(["3","-4","+"])) # -1