from itertools import product
from string import ascii_lowercase, printable

m=int(input())
d=input().split()

for k in product(ascii_lowercase,repeat=3):
    for i in range(m):
        if chr(int(d[i])^ord(k[i%len(k)]))not in" ();:,.'?-"+printable[:63]:
            break
    else:
        print("".join(k))
        break