/*   素數(shù)篩選法B 
      崔恒
   */

#include <iostream.h>
#include <math.h>
#define n 10000000001
bool prime[n];

void main()
{
	int i,j,x,q,k;
	cout<<"優(yōu)化算法B,請輸入一個數(shù):";
	cin>>x;
	if (x%2==0) q=x/2-2;
     else q=(x+1)/2-2;
	for (i=0;i<=q;i++)
		prime[i]=true;

    for(i=0; 2*i+3<=sqrt(x); i++)
	{	
		j=i*(2*i+6)+3;
		k=(j-i)/(2*i+3);
		if  (prime[i])
		
		while(j<=q)
		{
		prime[j]=false;
		k++; 
		j=k*(2*i+3)+i;
		 }
		
	}
	cout<<"   "<<x<<"內(nèi)的所有的素數(shù)為:"<<endl<<"2"<<endl; 
    k=1;
	for(i=0;i<=q;i++)	
	{   
       
		if (prime[i]) 
		{
			cout<<i*2+3<<"           ";
			if(k%5 == 0) cout<<endl;
            k++;
		}
    }

}