#!/bin/python3

import sys


h = [int(h_temp) for h_temp in input().strip().split(' ')]
word = input().strip()

mx = h[0]
n = len(word)
for i in range(n):
    id = ord(word[i])-ord('a')
    mx = max(mx,h[id])

mx = mx*len(word)
print(mx)