CF1147B.Chladni Figure
普及/提高-
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题目描述
Inaka has a disc, the circumference of which is n units. The circumference is equally divided by n points numbered clockwise from 1 to n , such that points i and i+1 ( 1≤i<n ) are adjacent, and so are points n and 1 .
There are m straight segments on the disc, the endpoints of which are all among the aforementioned n points.
Inaka wants to know if her image is rotationally symmetrical, i.e. if there is an integer k ( 1≤k<n ), such that if all segments are rotated clockwise around the center of the circle by k units, the new image will be the same as the original one.
输入格式
The first line contains two space-separated integers n and m ( 2≤n≤100000 , 1≤m≤200000 ) — the number of points and the number of segments, respectively.
The i -th of the following m lines contains two space-separated integers ai and bi ( 1≤ai,bi≤n , ai=bi ) that describe a segment connecting points ai and bi .
It is guaranteed that no segments coincide.
输出格式
Output one line — "Yes" if the image is rotationally symmetrical, and "No" otherwise (both excluding quotation marks).
You can output each letter in any case (upper or lower).
输入输出样例
输入#1
12 6 1 3 3 7 5 7 7 11 9 11 11 3
输出#1
Yes
输入#2
9 6 4 5 5 6 7 8 8 9 1 2 2 3
输出#2
Yes
输入#3
10 3 1 2 3 2 7 2
输出#3
No
输入#4
10 2 1 6 2 7
输出#4
Yes
说明/提示
The first two examples are illustrated below. Both images become the same as their respective original ones after a clockwise rotation of 120 degrees around the center.