import sys
sys.set_int_max_str_digits(0)

N = int(input())
P = list(map(int, input().split()))

ans = 1

for p in P:
    ans *= sum(int(_p) for _p in str(p))

if ans >= 10:
    while ans >= 10:
        ans = sum(map(int, str(ans)))

print(ans)