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 Rust (1.15.1) (judge verdict: Accepted)

fn main() {
    let mut N = String::new();
    std::io::stdin().read_line(&mut N).expect("Fail get N");
    let N: u8 = N.trim().parse().expect("Fail N parse");
    
    let answer = match N % 2 {
        0 => 0.5,
        1 => (N + 1) as f64 / (2 * N) as f64,
        _ => -1.0,
    };
    println!("{}", answer);
}