from fractions import Fraction as frac
input()
a = list(map(int,input().split()))
sm = frac("1/" + str(a[0]))
for i in range(1,len(a)):
    sm += frac("1/" + str(a[i]))
print(sm.denominator / sm.numerator)
3553fa1ec016c3c3beb36281ef3b241175889be0
<mask token>

<mask token>
input()
<mask token>
for i in range(1, len(a)):
    sm += frac('1/' + str(a[i]))
print(sm.denominator / sm.numerator)

<mask token>
input()
a = list(map(int, input().split()))
sm = frac('1/' + str(a[0]))
for i in range(1, len(a)):
    sm += frac('1/' + str(a[i]))
print(sm.denominator / sm.numerator)

from fractions import Fraction as frac
input()
a = list(map(int, input().split()))
sm = frac('1/' + str(a[0]))
for i in range(1, len(a)):
    sm += frac('1/' + str(a[i]))
print(sm.denominator / sm.numerator)

from fractions import Fraction as frac
input()
a = list(map(int,input().split()))
sm = frac("1/" + str(a[0]))
for i in range(1,len(a)):
    sm += frac("1/" + str(a[i]))
print(sm.denominator / sm.numerator)