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 Go (1.6) (judge verdict: Accepted)

package main
import (
  "fmt"
)
func main() {
  var n,x,m,y int64
  fmt.Scan(&n,&x)
  if n%2 == 0 && x == n/2 {
    m = n + x
  } else if x <= n/2 {
    m = n + 2*x
    y = n - 2*x
    for {
      if x%y == 0 {
        m += 2*x - y
        break
      }
      m += 2*(x/y)*y
      x,y = y,x%y
    }
  } else {
    y = n - x
    m = n
    for {
      if x%y == 0 {
        m += 2*x - y
        break
      }
      m += 2*(x/y)*y
      x,y = y,x%y
    }
  }
  fmt.Println(m)
}