#!/bin/python

import sys

def l_to_idx(l):
    return  ord(l) - ord('a') 

h = map(int,raw_input().strip().split(' '))
word = raw_input().strip()
width = len(word)
max_h = 0
for letter in list(word):
    height = h[l_to_idx(letter)]
    if height > max_h:
        max_h = height
area = width * max_h
print area