PROGRAMMING:Husky looking for square

Double eleven arrived, husky bought a lot of biscuits, because he wanted to be fat. But husky only eats square biscuits. You can help husky find biscuits!
Now I'll tell you the coordinates of the four points and ask if you can make a square with the four points as the vertices. If yes can be output, otherwise no can be output;
Because Husky's math is not very good, so I hope you can help him to eat his favorite biscuit;
input
###Input format:
There are multiple groups of input data. Input 8 integers, which are the coordinates ax, ay, BX, by, CX, cy, DX, dy of 4 points. (the absolute value of each number is less than 100). Input ensures that there is no case of 4 points being the same;
###Output format:
If you can form a square, output yes, otherwise output No.
###Input example:
Here is a set of inputs. For example:
```in
0 0 1 0 0 1 1 1
1 2 2 3 4 5 5 6
```
###Output example:
The corresponding output is given here. For example:
```out
yes
no
```







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