PROGRAMMING:[simple branch] [shape judgment B --]

Enter the coordinates (x1, Y1) and (X2, Y2) of the two points in the plane rectangular coordinate system. Please determine the specific shape of the quadrilateral composed of these two points. Take (x1, Y1) as the lower left corner and (X2, Y2) as the upper right corner.
###Input format:
Input x1, Y1, X2, Y2, which are all integers separated by spaces. The data guarantee that (x1, Y1) is the lower left corner and (X2, Y2) is the upper right corner to form a quadrilateral. All data are in the range of int.
###Output format:
If it can form a square, output yes, otherwise output No. after outputting data, output carriage return and line feed.
###Input sample 1:
Here is a set of inputs. For example:
```in
1 1 3 3
```
###Output sample 1:
The corresponding output is given here. For example:
```out
YES
```
###Input sample 2:
Here is a set of inputs. For example:
```in
1 1 3 5
```
###Output sample 2:
The corresponding output is given here. For example:
```out
No
```







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