def bitsum(n):
    s = str(n)
    ret = 0

    for i in s:
        ret += int(i)

    return ret


N = int(input())

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

now = 1
for i in range(N):

    now = bitsum(now)
    now *= P[i]


while now >= 10:

    now = bitsum(now)

print (now)