Problem:
Score : 100 points

Problem Statement

Given is an integer N.

Takahashi chooses an integer a from the positive integers not greater than N with equal probability.

Find the probability that a is odd.

Constraints

1 \leq N \leq 100

Input

Input is given from Standard Input in the following format:

N

Output

Print the probability that a is odd.
Your output will be considered correct when its absolute or relative error from the judge's output is at most 10^{-6}.

Sample Input 1

4

Sample Output 1

0.5000000000

There are four positive integers not greater than 4: 1, 2, 3, and 4. Among them, we have two odd numbers: 1 and 3. Thus, the answer is \frac{2}{4} = 0.5.

Sample Input 2

5

Sample Output 2

0.6000000000

Sample Input 3

1

Sample Output 3

1.0000000000

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

#pragma GCC optimize ("O3")
#include <bits/stdc++.h>
#define ll long long
#define cst first
#define dur second
#define IO ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
using namespace std;
const int N = 1e7 + 5, M = 2 * N + 5;

int main(){
    int n;
    cin >> n;
    int m = (n + 1) / 2;
    long double a = m, b = n;
    cout << fixed << setprecision(10) << a / b << endl;
}