#!/bin/python

import sys


h = map(int,raw_input().strip().split(' '))
word = raw_input().strip()
alphabet = dict()
for i,letter in enumerate('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()):
    alphabet[letter] = i

max_height = 0
for letters in word:
    if h[alphabet[letters]] > max_height:
        max_height = h[alphabet[letters]]
        
print max_height * len(word)