class Solution {

public:

    int titleToNumber(string s) {

        //the last bit of s, multiply 26

        //then left move 1 bit, multiply 26^2

        //iterate

        int len = s.length();

        int ret = ;

        int multiplier = ;

        int cur;

        for(int i = len-; i >= ; i--){

            cur = s[i]-'A'+;

            ret += cur*multiplier;

            multiplier *= ;

        }

        return ret;

    }

};