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# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;

namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            var val = Console.ReadLine().Split(' ');
            var a = long.Parse(val[0]);
            var b = long.Parse(val[1]);

            long max = a > b ? b : a;
            var h = new long[256];
            long v = 0;

            if (max > 1 && max <= 2)
            {
                h[v] = 2;
                v++;
            }

            for (long num = 3; num < max; num++)
            {
                if (num % 2 == 0) continue;

                if (a % num == 0 && b % num == 0)
                {

                    bool t = false;
                    foreach (long i in h)
                    {
                        if (i == 0) break;
                        if (num % i == 0) t = true;
                    }
                    if(t) continue;

                    // 素数である
                    h[v] = num;
                    v++;
                }
            }


            Console.Write(v+1);

        }
    }
}