# -*- coding:utf-8 -*-

class Solution:

    def StrToInt(self, s):

        # write code here

        if not s:

            return 0

        sign = 1

        if s[0] == '+' or s[0] == '-':

            if s[0] == '-':

                sign = -1

            s = s[1:]

        # 思路1

        # res = 0

        # for x in s:

        #     if x > '9' or x < '0':

        #         return 0

        #     res = res * 10 + ord(x)- 48

        # return res * sign

        # 思路2：

        dict = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}

        res = 0

        for x in s:

            if x > '9' or x < '0':

                return 0

            res = res * 10 + dict[x]

        return res * sign

if __name__ == '__main__':

    result = Solution().StrToInt('-123')

    print(result)