def func(x):
    ret = 0
    while x > 0:
        ret += (x % 10)
        x //= 10
    return ret

def func2(x):
    ret = 0
    while x > 0:
        ret += 1
        x //= 10
    return ret

n = int(input())
a = list(map(int,input().split()))
sum = 1
for i in range(n):
    sum *= a[i]
    
while func2(sum) > 1:
    sum = func(sum)
    
print(sum)