Problem Statement  
Consider the following set (see notes for clarification):S = { p/q  w <= p <= x, y <= q <= z }Given w, x, y, and z return the number of distinct elements in S.  
Definition  
 
Notes  
  S is the set of all rational numbers whose numerators are between w and x inclusive, and whose denominators are between y and z inclusive.  
Constraints  
  x and z will be between 1 and 100, inclusive.  
  w will be between 1 and x, inclusive.  
  y will be between 1 and z, inclusive.  
Examples  
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