N = int(input())
lsP = input().split()
def func(p):
    ls = list(p)
    while len(ls) >= 2:
        wa = [int(a) for a in ls]
        ls = list(str(sum(wa)))
    return ls[0]
if '0' in lsP:
    print(0)
    exit()
ans = 1
for i in range(N):
    ans *= int(func(lsP[i]))
    ans = func(str(ans))
print(ans)