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 in C++14 (GCC 5.4.1) (judge verdict: Accepted)

//#include "stdc++.h"
#include<bits/stdc++.h>
#include<iostream>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ldb;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef pair <ll, int> pli;
typedef pair <db, db> pdd;
typedef vector<int> vi;
#define m1 make_pair
#define pb push_back
#define flush fflush(stdout)
#define IOS std::ios::sync_with_stdio(false); cin.tie(NULL);cout.tie(NULL);
#define reset(x,v) memset(x,v,sizeof(x))
#define sz(x) (int)(x.size())
#define ff first
#define ss second
#define endl "\n"
#define int long long int
inline ll gcd(ll a,ll b){if(a==0) return b;return gcd(b%a,a);}
inline ll power(ll a,ll n,ll m){if(n==0)return 1;ll p=power(a,n/2,m);p=(p*p)%m;if(n%2) return (p*a)%m;else return p;}
const ll MOD = 1000000007;
const ll mod=1000000006;
const int INF = 0x3f3f3f3f;
const ll LL_INF = 0x3f3f3f3f3f3f3f3f;
/*
 shuffle(x,x+n,rng) // shuffling elements of x in random order
 */

int32_t main()
{
    IOS;
    int n;
    cin>>n;
    int a[n];long double ans,sum=0.0;
    for(int i=0;i<n;i++)
    { cin>>a[i];
        sum=sum+(long double)1/a[i];
    }
    ans=1.0/sum;
    cout<<ans<<endl;
    
    return 0;
}