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)

use std::io;
use std::io::Write;

fn main() {
    let mut input = String::new();

    io::stdin().read_line(&mut input)
        .expect("Failed to read line");

    let input: u32 = input.trim().parse()
        .expect("Expected a number");

    if input == 1 {
        print!("{}", 1.0);
        io::stdout().flush().unwrap();
    } else if input % 2 == 0 {
        print!("{}", 0.5);
        io::stdout().flush().unwrap();
    } else {
        print!("{}", ((input/2)+1) as f64 / input as f64);
        io::stdout().flush().unwrap();
    }
}