程序代码：

#include<iostream>
#define MAX 1000001
using namespace std;
int a[MAX];
int main()
{
   int n,i,j,m=1;
   memset(a,0,sizeof(a));
   for(i=2;i<MAX;i++)
      if(a[i]==0)
      {for(j=i;j<MAX;j+=i)a[j]=m;m++;}  
   while(scanf("%d",&n)!=EOF)
   {printf("%d\n",a[n]);}  
   return 0;
}

程序代码：

#include<iostream>
#include <windows.h>
#define MAX 1000001
using namespace std;
int a[MAX];

int ss(int n)
{
   int i, flag;

   for (i = 2; i < n; i++)
   {
           if (n % i == 0)
           {             
               flag = 0;
                break;
           }
   }
           if (i == n)
               flag = 1;
      
      return flag;
}
int main()
{
   int i,j,m=1, count = 0;
   memset(a,0,sizeof(a));
   for(i=2;i<MAX;i++)
      if(a[i]==0)
      {for(j=i;j<MAX;j+=i)a[j]=m;m++;} 
      i = 2;
   while(i < MAX)
   {
       if (ss(i))
       {
           printf("第%d个素数是%d\n", a[i], i);
           count++;
       }
       i++;
       if (count % 36 == 0)
           system("pause");
   }
   return 0;
}