#!/bin/python

import sys

def get_selection_area(word, h):
    max_height = -float('inf')
    for c in word.lower():
        max_height = max(max_height, h[ord(c)-97])
    return max_height * len(word)

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