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 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>

#define num_max(p,q)((p)>(q)?(p):(q))
#define num_min(p,q)((p)<(q)?(p):(q))
int cmp(const void *a, const void *b)
{
	return *(int*)a - *(int*)b;//昇順
	 //降順ならreturn *(int*)b - *(int*)a;
}
int main()
{
	int N;
	scanf("%d", &N);
	if(N%2==0)printf("0.500000000\n");
	else printf("%lf\n", (double)((N / 2)+1) / N);
	return 0;
}