Problem:
 Score : 200 points    Problem Statement Given is a sequence of N integers A_1, \ldots, A_N .  Find the (multiplicative) inverse of the sum of the inverses of these numbers, \frac{1}{\frac{1}{A_1} + \ldots + \frac{1}{A_N}} .      Constraints  1 \leq N \leq 100  1 \leq A_i \leq 1000         Input Input is given from Standard Input in the following format:  N  A_1  A_2  \ldots  A_N       Output Print a decimal number (or an integer) representing the value of \frac{1}{\frac{1}{A_1} + \ldots + \frac{1}{A_N}} .  Your output will be judged correct when its absolute or relative error from the judge's output is at most 10^{-5} .        Sample Input 1 2
10 30      Sample Output 1 7.5  \frac{1}{\frac{1}{10} + \frac{1}{30}} = \frac{1}{\frac{4}{30}} = \frac{30}{4} = 7.5 .  Printing 7.50001 , 7.49999 , and so on will also be accepted.       Sample Input 2 3
200 200 200      Sample Output 2 66.66666666666667  \frac{1}{\frac{1}{200} + \frac{1}{200} + \frac{1}{200}} = \frac{1}{\frac{3}{200}} = \frac{200}{3} = 66.6666... .  Printing 6.66666e+1 and so on will also be accepted.       Sample Input 3 1
1000      Sample Output 3 1000  \frac{1}{\frac{1}{1000}} = 1000 .  Printing +1000.0 and so on will also be accepted.

Solution (Python):
n=int(input())
A=list(map(int,input().split()))
ans=0
for a in A:
    ans+=1/a
print(1/ans)

Solution (Python):
import sys
input = sys.stdin.readline

N = int(input())
A = list(map(int, input().split()))
den = 0
for value in A:
    den += 1 / value
print(1 / den)

Solution (Python):
N = int(input())
A = list(map(int, input().split()))

ans = 0
for i in range(N):
  ans += 1 / A[i]

print(1 / ans)

Solution (Python):

import sys
sys.setrecursionlimit(300000)


def solve(N: int, A: "List[int]"):
    tmp = 0
    for a in A:
        tmp += 1 / a
    ret = 1 / tmp
    print(ret)
    return


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  
    A = [ int(next(tokens)) for _ in range(N) ]  
    solve(N, A)

if __name__ == '__main__':
    main()

Solution (Python):
import sys
sys.setrecursionlimit(10000000)
def input():
    return sys.stdin.readline()[:-1]
from bisect import *
from collections import *
from heapq import *
from math import *
from itertools import *

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

Solution (Python):

import sys
INF = float("inf")


def solve(N: int, A: "List[int]"):
    tot = 0
    for a in A:
        tot += 1/a
    tot = 1/tot
    print(tot)
    return


def main():

    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  
    A = [int(next(tokens)) for _ in range(N)]  
    solve(N, A)


if __name__ == '__main__':
    main()

Solution (Python):
n = int(input())
a = list(map(int, input().split()))

ans = 0
for ai in a:
    ans += 1/ai

print(1/ans)

Solution (Python):
N = int(input())
A = [1 / int(i) for i in input().split()]

print("{:.9f}".format(1 / sum(A)))

Solution (Python):
n = int(input())
a = list(map(int,input().split()))
res = 0
for i in a:
    res += 1 / i
print(1 / res)

Solution (Python):

from collections import defaultdict,deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return [int(x) for x in sys.stdin.readline().split()]
def I(): return int(sys.stdin.readline())
def LS():return [list(x) for x in sys.stdin.readline().split()]
def S():
    res = list(sys.stdin.readline())
    if res[-1] == "\n":
        return res[:-1]
    return res
def IR(n):
    return [I() for i in range(n)]
def LIR(n):
    return [LI() for i in range(n)]
def SR(n):
    return [S() for i in range(n)]
def LSR(n):
    return [LS() for i in range(n)]

sys.setrecursionlimit(1000000)
mod = 1000000007


def A():
    a = I()
    s = S()
    if a >= 3200:
        print(s)
    else:
        print("red")
    return


def B():
    n = I()
    a = LI()
    ans = 0
    for i in a:
        ans += 1/i
    print(1/ans)
    return


def C():

    return


def D():

    return


def E():

    return


def F():

    return


if __name__ == "__main__":
    B()