import numpy as np

n=int(eval(input()))

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



lista=0

for i in range(n):

    lista=lista+1/a[i]

print((1/lista))

n=int(eval(input()))

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

 

lista=0

for i in range(n):

    lista=lista+1/a[i]

print((1/lista))

import numpy as np

n = int(eval(input()))
a = list(map(int, input().split()))
lista = 0
for i in range(n):
    lista = lista + 1 / a[i]
print((1 / lista))

n = int(eval(input()))
a = list(map(int, input().split()))
lista = 0
for i in range(n):
    lista = lista + 1 / a[i]
print((1 / lista))

-import numpy as np -