#!/bin/python

import sys


h = map(int,raw_input().strip().split(' '))
word = list(raw_input().strip())
maxi=0
for i in range(0,len(word)):
    if maxi<h[ord(word[i])-ord('a')]:
        maxi=h[ord(word[i])-ord('a')]
print maxi *len(word)