n = int(input())
fig_ls = list(map(int, input().split()))
sum_fig = 1
for i in range(n):
    sum_fig*=fig_ls[i]
sum_str = str(sum_fig)
#print(sum_str)
while len(sum_str) > 1:
    age  = 0
    for a in sum_str:
        age+=int(a)
    sum_str = str(age)

print(age)