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.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            // スペース区切りの整数の入力
            long[] D = Console.ReadLine().Split().Select(long.Parse).ToArray();

            long N, a, b, l, out1;
            N = D[0];
            b = D[1];
            a = N - b;
            l = Math.Abs(N - b);

            out1 = N;

            while (l != 0)
            {
                if (a > b)
                {
                    if (b == 1)
                    {
                        out1 = out1 + 2* (a - 1);
                        break;
                    }
                    else
                    {
                        a = a - b;
                        out1 = out1 + 2 * b;
                    }
                }
                else if(a < b)
                {
                    if (a == 1)
                    {
                        out1 = out1 + 2 * (b - 1);
                        break;
                    }
                    else
                    {
                        b = b - a;
                        out1 = out1 + 2 * a;
                    }
                }
                l = Math.Abs(b - a);
            }
            out1 = out1 + a;
            Console.WriteLine(out1);
        }
    }
}