Simple mathematical solution. The way we calculate the value of a number using units and tens places.

eg : 121 = 1* 10^2 + 2* 10^1 + 1* 10^0

Similarly : AB = A*26^1 + B*26^0. Here base is taken as 26 instead of 10. and replace the value of A-Z as 1-26.

```
import string
import math
class Solution(object):
def getDictionary(self):
D = {}
for i , alphabet in enumerate(string.ascii_uppercase):
D[alphabet] = i+1
return D
def titleToNumber(self, s):
"""
:type s: str
:rtype: int
"""
alphabtes = self.getDictionary()
sum = 0
for i , a in enumerate(s[::-1]):
val = alphabtes[a] * (math.pow(26,i))
sum = sum + val
return int(sum)
```