a = map(int,raw_input().split())
s = raw_input()
d = dict()
al = "abcdefghijklmnopqrstuvwxyz"
for i in range(26):
    d[al[i]] = a[i]
m = 0
for i in s:
    if m<d[i]:
        m = d[i]
print m*len(s)