#include<stdio.h>
int n;
int t;

char a[1000005];

int main()
{long suma=0;
 freopen("fractii.in","r",stdin);
 freopen("fractii.out","w",stdout);
 scanf("%d ",&n);
 int i,j=0;
  for(i=2;i<=n;i++)  
       if(!a[i])  
       { t++;suma++;  
         
        for(j=i;j<=n;j+=i)  
           {a[j]=1;suma++; }    
       }    
 
	
  printf("%d ",n*n-suma); 
 return 0;
}