问题 I: Mysterious Light
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≦1012 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.
输入
The input is given from Standard Input in the following format:N X
输出
Print the total length of the ray’s trajectory.
样例输入 Copy
5 2
样例输出 Copy
12
提示
Refer to the image in the Problem Statement section. The total length of the trajectory is 2+3+2+2+1+1+1=12. 思路:就是列出来一部分 找出规律。 代码:
#include
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