Roman Integers are represented as I-1;V-5;X-10;L-50;C-100;D-500;M-1000

Generally Roman numbers are added from left to right to get its equivalent integer.

However in certain cases, if the preceding letter is lesser than the current letter, the two numbers are

subtracted. Eg:

399 = CCCXCIX

(100+100+100+(100-10)+(10-1))=399

```
dict={"I":1,"V":5,"X":10,"L":50,"C":100,"D":500,"M":1000}
res=0
i=0
res = 0
i = 0
while i < len(s):
if i+1<len(s) and dict[s[i]] < dict[s[i + 1]]:
res += dict[s[i + 1]] - dict[s[i]]
i+= 2
else:
res += dict[s[i]]
i += 1
return res
```