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

K = 1
for p in P:
    K *= p

age = 0
for k in str(K):
    age += int(k)

while len(str(age)) > 1:
    tmp = age
    age = 0
    for k in str(tmp):
        age += int(k)

print(age)