#!/bin/python

import sys


h = map(int,raw_input().strip().split(' '))
m = {}
for i in range(ord('a'), ord('z') + 1):
    m[chr(i)] = h[i - ord('a')]
word = raw_input().strip()
length = len(word)
height = 0
for c in word:
    if(m[c] > height):
        height = m[c]
print height * length