Analysis of Pat computer questions in Zhejiang University 1007. Prime Number pair conjecture (20)

1007. Conjecture of prime number pairs (20) Time Limit 400 MS
Memory limit 32000 KB
CodeLength limit 8000 B
JudgementProgram Standard Author Chen, Yue

Let's define DN as: DN = pN + 1-PN, where Pi is the I prime number. Obviously, d1 = 1 and for n> 1, dn is an even number. The "prime number pair conjecture" considers "There are infinite numbers of adjacent prime numbers with a difference of 2 ".

Given any positive integer N (<105), calculate the number of prime number pairs that do not exceed n.

Input Format:Each test input contains one test case and a positive integer n.

Output Format:The output of each test case occupies one row. The number of prime number pairs that meet the conjecture cannot exceed n.

Input example:

 
20
 

Output example:

 
4
 

 
 # include 
   
     # include 
    
      # include 
     
       # include 
      
        # define maxsize 100000 using namespace STD; int prime [maxsize]; int main () {memset (Prime, 0, maxsize); int N, I, j; int K = 0; vector 
       
         VEC; vector 
        
         : iterator it1, it2; int M = (INT) (SQRT (double (maxsize) + 0.5); CIN> N; for (I = 2; I