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>
using namespace std;
using ll = long long;
#define rep(i,n) for(ll i=0, i##_len=(n); i<i##_len; ++i)
#define repin(a,n) vector<ll> a(n);rep(i,n){cin>>a[i];}
#define repins(a,n) vector<string> a(n);rep(i,n){cin>>a[i];}
#define repind(a,n) vector<double> a(n);rep(i,n){cin>>a[i];}
#define in(a) ll a;cin>>a;
#define ins(a) string a;cin>>a;
#define ind(a) double a;cin>>a;
template<class T>
inline void out(T a){cout<<a<<endl; }
inline void out(double a){ printf("%.10f\n", a);} 
#define all(x) (x).begin(),(x).end()
#define rep2(i,a,b) for(ll i=(a);i<(b);++i)
#define range(i,s,c) for(ll i=(s);i<(s+c);++i)
using vell = vector<ll>;
using ves = vector<string>;
using ved = vector<double>;

ll mod = 1000000007;

ll mmul(ll a, ll b) { return ((a % mod) * (b % mod)) % mod;}

ll mpow(ll a, ll b) {
	if (b == 0) return 1;
	if (b % 2 == 0) {
		ll d = mpow(a, b / 2);
		return (d * d) % mod;
	}
	return (a * mpow(a, b - 1)) % mod;
}

ll mdiv(ll a, ll b) { return mmul(a, mpow(b, mod - 2)); }

int main()
{
	in(n);

	if(n%2==0){
		out(0.5);
	}else{
		out(ceil(n/2.0)/n);
	}
}