n = int(input())
p = list(map(int,input().split()))
ans = 1
for i in range(n):
    ans *= p[i]
    while ans >= 10:
        str_ans = str(ans)
        str_ans_list = list(str_ans)
        wa = 0
        for j in range(len(str_ans_list)):
            wa += int(str_ans_list[j])
            ans = wa
print(ans)