Problem:
Score : 500 points

Problem Statement

Snuke is conducting an optical experiment using mirrors and his new invention, the rifle of Mysterious Light.

Three mirrors of length N are set so that they form an equilateral triangle.
Let the vertices of the triangle be a, b and c.

Inside the triangle, the rifle is placed at the point p on segment ab such that ap = X.
(The size of the rifle is negligible.)
Now, the rifle is about to fire a ray of Mysterious Light in the direction of bc.

The ray of Mysterious Light will travel in a straight line, and will be reflected by mirrors, in the same ways as "ordinary" light.
There is one major difference, though: it will be also reflected by its own trajectory as if it is a mirror!
When the ray comes back to the rifle, the ray will be absorbed.

The following image shows the ray's trajectory where N = 5 and X = 2.

It can be shown that the ray eventually comes back to the rifle and is absorbed, regardless of the values of N and X.
Find the total length of the ray's trajectory.

Constraints

2≦N≦10^{12}

1≦X≦N-1

N and X are integers.

Partial Points

300 points will be awarded for passing the test set satisfying N≦1000.

Another 200 points will be awarded for passing the test set without additional constraints.

Input

The input is given from Standard Input in the following format:

N X

Output

Print the total length of the ray's trajectory.

Sample Input 1

5 2

Sample Output 1

12

Refer to the image in the Problem Statement section.
The total length of the trajectory is 2+3+2+2+1+1+1 = 12.

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;

public class Don
{
    public Don() { }
    private Reader r = new Reader();

    public void Solve()
    {
        var N = r.nextLong();
        var X = r.nextLong();
        if (N % 2 == 0)
        {
            if (X == N / 2)
            {
                Console.WriteLine(X * 3);
            } else if (X % 2 == 0)
            {
                Console.WriteLine((N - 2) * 3);
            } else
            {
                Console.WriteLine((N - 1) * 3);
            }

        } else
        {
            Console.WriteLine((N - 1) * 3);
        }

    }

    public static void Main(string[] args)
    {
        new Don().Solve();
    }

}

class Reader
{
    string[] s;
    int i;
    char[] cs = new char[] { ' ' };

    public Reader()
    {
        s = new string[0];
        i = 0;
    }

    public string next()
    {
        if (i < s.Length)
            return s[i++];
        var input = Console.ReadLine();
        while (input == "")
            input = Console.ReadLine();
        s = input.Split(cs, StringSplitOptions.RemoveEmptyEntries);
        i = 0;
        return next();
    }

    public int nextInt()
    {
        return int.Parse(next());
    }

    public long nextLong()
    {
        return long.Parse(next());
    }

    public double nextDouble()
    {
        return double.Parse(next());
    }

}