$0  file1 file2 file3 file4 

  Performs similar things to draw the venn diagram for 4 sets. 
  Each file given is regarded as a set that consists of 
  the elements; an element is a character string separated by
  line ending characters.  The venn diagram can be drawn 
  using 4 rectangles or 4 ovals so this program utilizes this 
  mathematical theorem.

 Options : 
   -= : skip reading the first line of every 4 files.
   -b : skip blank lines.
   -x : Also adds 10 x 10 table to the ouput. You can easily understand it.