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 Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.util.*;
class Main {
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        long a = sc.nextLong();
        long b = sc.nextLong();
        long wk_no = a < b ? a : b;
        int cont = 0;
       
        for(long i = 1 ;i <= wk_no/2 ; i++){
            if(a%i == 0 && b%i == 0){
                if(is_prime(i)) {
                  if(i == 1){
                    cont ++;
                  }else{
                     cont += 2;
                   }
                  }
            }
        }
        
        System.out.println(cont);
        sc.close();
    }
    static boolean is_prime(long n) {
        if(n == 1) return true;
        for(long i = 2; i*i <= n; ++i) { // 2 <= i <= sqrt(n) に約数があれば、
            if(n % i == 0) return false; // n は素数ではない
        }
        return true;
    }
}