public class Solution {
    public int titleToNumber(String s) {
        int sum = 0;
        for(int i = s.length()-1; i >= 0; i--) {
            char cur = s.charAt(i);
            int mult = s.length() - 1 - i;
            sum += Math.pow(26,mult)*(cur - 'A' + 1);
        }
        return sum;
    }
}