13.Roman to Integer 

class Solution:
    def romanToInt(self, s: str) -> int:
        dic = {}
        dic["I"] = 1
        dic["V"] = 5
        dic["X"] = 10
        dic["L"] = 50
        dic["C"] = 100
        dic["D"] = 500
        dic["M"] = 1000
        dic["IV"] = 4
        dic["IX"] = 9
        dic["XL"] = 40
        dic["XC"] = 90
        dic["CD"] = 400
        dic["CM"] = 900

        number = 0
        index = 0
        while 1:
            if index +1 == len(s):
                number = number + dic[s[index]]
                return number
            elif index > len(s)-1:
                return number
            else:
                s_key = s[index : index+2]
                if s_key in dic:
                    number = number + dic[s_key]
                    index = index + 2
                else:
                    number = number + dic[s[index]]
                    index = index + 1