Problems
Quadrilateral - 2
Quadrilateral - 2
Four points are given on the plane. Do they form a square?
\InputFile
Four lines, each of them contain two numbers - the coordinates of given points. The input data are integers and do not exceed \textbf{1000} by the absolute value.
\OutputFile
If the given points are vertices of a square print "\textbf{YES}", otherwise print "\textbf{NO}".
Input example #1
0 0 1 1 0 1 1 0
Output example #1
YES