#!/bin/python3

import sys


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

width = len(word)

max_height = 0
for i in range(0, width):
    j = ord(word[i]) - ord('a')
    if max_height < h[j]:
        max_height = h[j]

print(width * max_height)