from decimal import Decimal

n=int(eval(input()))

List=list(map(int,input().split()))

add=0

for i in List:

    add+=Decimal(1/i)

print((Decimal(1/add)))
n=int(eval(input()))

List=list(map(int,input().split()))

add=0

for i in List:

    add+=1/i

print((1/add))
from decimal import Decimal

n = int(eval(input()))
List = list(map(int, input().split()))
add = 0
for i in List:
    add += Decimal(1 / i)
print((Decimal(1 / add)))

n = int(eval(input()))
List = list(map(int, input().split()))
add = 0
for i in List:
    add += 1 / i
print((1 / add))

-from decimal import Decimal - -    add += Decimal(1 / i) -print((Decimal(1 / add))) +    add += 1 / i +print((1 / add))