#!/bin/python

import sys


h = map(int,raw_input().strip().split(' '))
word = raw_input().strip()
letters = 'a b c d e f g h i j k l m n o p q r s t u v w x y z'.split(' ')
let_dict = {}
for i, l in enumerate(letters):
    let_dict[l] = i
max_height = 0
for i in word:
    if max_height < h[let_dict[i]]:
        max_height = h[let_dict[i]]
print max_height * len(word)