Problem Statement  
A prime number is an integer greater than 1 that has no positive divisors other than 1 and itself. The first prime numbers are 2, 3, 5, 7, 11, 13, 17, ... The number N is considered far from primes if there are no prime numbers between N10 and N+10, inclusive, i.e., all numbers N10, N9, ..., N1, N, N+1, ..., N+9, N+10 are not prime. You are given an int A and an int B. Return the number of far from primes numbers between A and B, inclusive.  
Definition  
 
Constraints  
  A will be between 10 and 100000, inclusive.  
  B will be between A and 100000, inclusive.  
  (B  A) will be between 0 and 1000, inclusive.  
Examples  
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