#include <string>
class Solution {
private:
    constexpr int numericValue(char c) {
        return (int) (c-'A');
    }
public:
    int titleToNumber(std::string columnTitle) {
        int value = 0;
        int length = columnTitle.length();
        for (long power = 1, i = length-1; i >= 0; power *= 26, i--) {
            // value += power;
            // value += power * numericValue(columnTitle.at(i));
            value += power * (1 + numericValue(columnTitle.at(i)));
        }
        return value;
    }
};