#include<fstream>
using namespace std;
ifstream in("fractii.in"); 
ofstream out("fractii.out");
long v[1000000];
int main ()
{  
	int i,n,s=0,j; 
	 in>>n; 
	for(i=3;i<=n;i++)
		{if(v[i]==0)
			for(j=i*i;j<=n;j=j+i) 
            v[j]=1; 
                
		} 
	for(i=1;i<=n;i++)		
        if(v[i]==0) 
            s++; 
out<<n*s-n+1; 		 
}