class Solution:
def romanToInt(self, s: str) -> int:
num_dict = {'I':1,'IV':4,'V':5,'IX':9,'X':10,'XL':40,'L':50,
'XC':90,'C':100,'CD':400,'D':500,'CM':900,'M':1000}
left,right = 0,2
res = 0
last = len(s)
while right < last+2:
tar = num_dict.get(s[left:right])
if tar:
res += tar
left += 2
right += 2
else:
res += num_dict.get(s[left])
left += 1
right += 1
return res