N = int(eval(input()))

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

rev_ans = 0

for a in A:

    rev_ans += 1 / a

ans = 1 / rev_ans

print(ans)
N = int(eval(input()))

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

ans = 1 / sum([1 / x for x in A])

print(ans)
N = int(eval(input()))
A = list(map(int, input().split()))
rev_ans = 0
for a in A:
    rev_ans += 1 / a
ans = 1 / rev_ans
print(ans)

N = int(eval(input()))
A = list(map(int, input().split()))
ans = 1 / sum([1 / x for x in A])
print(ans)

-rev_ans = 0 -for a in A: -    rev_ans += 1 / a -ans = 1 / rev_ans +ans = 1 / sum([1 / x for x in A])