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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
#define INF 2147483647
#define inf 1000000007
#define SYOU(x) setprecision(x)
#define abs(x,y) (max(x,y)-min(x,y))
#define mp make_pair
#define fi first
#define se second
using namespace std;
bool i[111100];
vector<int> ii;
signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  long long a,b,c,d=1,e=1,f=0,g=1,h=1,j;
  double w;
  cin >>w;
  a=w;
  if(a%2==1) w=(a/2+1)/w;
  else
  w=w/2/w;
  cout <<fixed<<w<<'\n';
  return (0);
}