def get_digit_sum(n):
    result = 0
    while n > 0:
        result += n % 10
        n //= 10
    return result


def main():
    length = int(input())
    sequence = [get_digit_sum(int(x)) for x in input().split()]
    product = 1
    for seq in sequence:
        product *= seq
    print(get_digit_sum(product))


if __name__ == '__main__':
    main()