#include<fstream.h>
#define N 1000001
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int s[N],t[N];
int main() {
int i,j,n,cu;
long long nr=0,sx=0,k;
fin>>n;
for(i=2;i*i<=n;i++)
	if(s[i]==0) {
		for(j=2;j*i<=n;j++) s[i*j]++;
		j=j-2; t[i]=j;
		}
for(;i<=n/2;i++)
	if(s[i]==0) {
		j=n/i;
		t[i]=j-1;
		}
for(i=2;i<=n/2;i++)
if(s[i]==0) {
k=t[i];
sx+=k*(k+1)/2;
}
for(i=4;i<=n/2;i++)
if(s[i]>1) sx-=s[i]-1;
sx*=2;
sx+=n-1;
nr=n;
nr*=n;
nr-=sx;
fout<<nr;
return 0;
}