Processing math: 100%

Problem H. Right triangle

Author:А. Лепёха   Time limit:1 sec
Input file:Standard input   Memory limit:512 Mb
Output file:Standard output  

Statement

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 right-angled.

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 right-angled triangle.

Input format

First line of input contains integers x1 and y1, second line contains integers x2 and y2, third line contains integers x3 and y3 — coordinates of three points. All points are pairwise different.

Output format

Output must contain YES, if given points form right triangle or NO otherwise.

Constraints

104xi,yi104

Sample tests

No. Standard input Standard output
1
0 0
0 8
6 0
YES
2
1 2
3 2
4 1
NO

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