n = int(input())
a = list(map(int, input().split()))
s = 0
for x in a:
    s += 1.0 / x
s = 1.0 / s
print('{:.9f}'.format(s))

4398309ed2f069e7ffb24c349ac2df1f96e966c5
<mask token>

<mask token>
for x in a:
    s += 1.0 / x
<mask token>
print('{:.9f}'.format(s))

n = int(input())
a = list(map(int, input().split()))
s = 0
for x in a:
    s += 1.0 / x
s = 1.0 / s
print('{:.9f}'.format(s))
