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 (1.42.0) (judge verdict: Accepted)

fn main() {
    let n: i32 = read_line_as_value();
    if n % 2 == 0 {
        println!("0.5");
    } else {
        println!("{:?}", ((n/2)+1) as f32 / n as f32);
    }
}

fn read_line_as_value<T: std::str::FromStr>() -> T {
    let mut input = String::new();
    let res = std::io::stdin().read_line(&mut input);
    if let Err(error) = res {
        panic!("io error at stdin.read_line: {}", error);
    };
    match input.trim().parse() {
        Ok(val) => val,
        _ => panic!("error while parsing input: {}", input)
    }
}