import numpy as np

n = int(eval(input()))

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

print((1.0/sum(1.0/a)))
n = int(eval(input()))

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

v = 0.0

for i in a:

    v += 1.0 / i

print((1.0 / v))
import numpy as np

n = int(eval(input()))
a = np.array(list(map(int, input().split())))
print((1.0 / sum(1.0 / a)))

n = int(eval(input()))
a = list(map(int, input().split()))
v = 0.0
for i in a:
    v += 1.0 / i
print((1.0 / v))

-import numpy as np - -a = np.array(list(map(int, input().split()))) -print((1.0 / sum(1.0 / a))) +a = list(map(int, input().split())) +v = 0.0 +for i in a: +    v += 1.0 / i +print((1.0 / v))