#!/bin/python

import sys

letras = "abcdefghijklmnopqrstuvwxyz"
h = map(int,raw_input().strip().split(' '))
word = raw_input().strip()
max = 0
for w in word:
    if(h[letras.index(w)]>max):
        max = h[letras.index(w)]
print(len(word)*max)