#include<fstream.h>
ifstream f("fractii.in");
ofstream g("fractii.out");
int n;
char a[1000001];
long long k;
void ciur(int x)
{int p=0;
	for(int i=x;i<=n;i+=x)
	{a[i]=1;p++;}
k+=2*(n-p-x);
}
int main()
{f>>n;
k=2*n-1;
ciur(2);
for(int i=3;i<=n;i+=2)
   if(!a[i])
	ciur(i);
   g<<k;
 return 0;
}