Problem Statement  
M integers are randomly independently chosen from the interval lowerBound...upperBound, inclusive. Return the probability that the Kth smallest element of the generated set is equal to N. K=1 refers to the smallest element, K=2 refers to the second smallest element, and so on.  
Definition  
 
Notes  
  The returned value must have an absolute or relative error less than 1e9.  
Constraints  
  M will be between 1 and 100, inclusive.  
  lowerBound will be between 1 and 1000, inclusive.  
  upperBound will be between lowerBound and 1000, inclusive.  
  N will be between lowerBound and upperBound, inclusive.  
  K will be between 1 and M, inclusive.  
Examples  
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