Author:  А. Лепёха  Time limit:  1 sec  
Input file:  Standard input  Memory limit:  512 Mb  
Output file:  Standard output 
Sasha graduated from high school and decided to enroll as a programmer at a local university. One of the first subjects in his course was «Geometry and Topology of Numbers». At the very first lecture, the whole group was asked to derive and prove a theorem that would make it possible to determine by three points on the plane whether the triangle formed by them is a rightangled.
Sasha was able to come up with several theorems, but for some reason his theorems give different answers. Write a program that, given the coordinates of three points, can correctly determine whether these points form a rightangled triangle.
First line of input contains integers x_{1} and y_{1}, second line contains integers x_{2} and y_{2}, third line contains integers x_{3} and y_{3} — coordinates of three points. All points are pairwise different.
Output must contain YES
, if given points form right triangle or NO
otherwise.
− 10^{4} ≤ x_{i}, y_{i} ≤ 10^{4}
No.  Standard input  Standard output 

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