import numpy as np



n = int(eval(input()))

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



reverse_list = []

for a in al:

    reverse_list.append(1/a)



print((1/sum(reverse_list)))

n = int(eval(input()))

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



reverse_list = []

for a in al:

    reverse_list.append(1/a)



print((1/sum(reverse_list)))

import numpy as np

n = int(eval(input()))
al = list(map(int, input().split()))
reverse_list = []
for a in al:
    reverse_list.append(1 / a)
print((1 / sum(reverse_list)))

n = int(eval(input()))
al = list(map(int, input().split()))
reverse_list = []
for a in al:
    reverse_list.append(1 / a)
print((1 / sum(reverse_list)))

-import numpy as np -