PROGRAMMING:Find the distance between two points

Define a point class, which has two data members: X and y, representing X and Y coordinates respectively, and has several member functions.
Define a function distance () to find the distance between two points.
###Input format:
There are two lines of input:
The first line is the X and Y coordinates of the first point;
The second line is the X and Y coordinates of the second point.
###Output format:
Output the distance between two points, retaining two decimal places.
###Input example:
0 9
3 -4
###Output example:
13.34






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