# たとえば12*23=(10+2)*(20+3)、桁和を求めるということは10は意味がなくなるので(1+2)*(2+3)となる
# つまり各数字の桁和の積でいいはず、式変形

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

def digitsum(n):
    calc = 0
    for s in str(n):
        calc += int(s)
    return calc

#digitsum(12)

P2 = []
for p in P:
    P2.append(digitsum(p))

#print(P2)

product = 1
for p in P2:
    product *= p

#print(product)

current = product
while len(str(current))>1:
    current = digitsum(current)
print(current)