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

num = 1
for i in P:
    num *= i


def digitSum(n):
    # 桁数を判定する
    if len(str(n)) is 1:
        return n
    dst = sum(list(map(int, str(n))))
    return digitSum(dst)


ans = digitSum(num)
print(int(ans))