class Solution(object):

    def titleToNumber(self, s):

        """

        :type s: str

        :rtype: int

        """

        res = 0

        for alpha in s:

            res = (ord(alpha) - 64) + res*26

        return res

class Solution(object):

    def titleToNumber(self, s):

        """

        :type s: str

        :rtype: int

        """

        def _map(ch):

            chn = ord(ch)

            assert chn >= ord('A') and chn <= ord('Z')

            return chn - ord('A') + 1

        lens = len(s)-1

        carry = 1

        val = 0

        while lens >=0:

            num = _map(s[lens])*carry

            val = val + num

            carry *= 26

            lens -= 1

        return val