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

def main():
    N = int(input())
    P = list(map(int, input().split()))
    A = 1
    for p in P:
        A *=  calc(p)
        A = calc(A)
    print(calc(A))

if __name__ == "__main__":
    main()