n = int(input())
a = list(map(int, input().split()))

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

k = 1
for i in range(n):
    k *= keta(a[i])
    k = keta(k)
print(keta(k))