#!/bin/python

import sys


h = map(int,raw_input().strip().split(' '))
word = raw_input().strip()

if len(word) == 0:
    print 0
    
area = 0
max_height = h[ord(word[0]) - ord('a')]
for ch in word:
    h1 = h[ord(ch) - ord('a')]
    if h1 > max_height:
        max_height = h1

print max_height*len(word)