Problem Statement  
A "Polyline" is a continuous line composed of one or more line segments. In a rectangle defined by four points (0,0), (a, 0), (a, b), and (0, b), we can draw a polyline starting from the point (x0, y0) to the end point (x1, y1) with at least one intersection point with each of the four edges of the rectangle. Write a class Polyline with a method length that returns the shortest length of such a polyline.  
Definition  
 
Notes  
  The polyline must not exceed the boundaries of the given rectangle.  
  The starting point and ending point may overlap.  
  Your return value must have an absolute or relative error less than 1e9.  
Constraints  
  a and b will be between 2 and 200 inclusive.  
  x0 and x1 will be between 1 and (a1) inclusive.  
  y0 and y1 will be between 1 and (b1) inclusive.  
Examples  
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