#include <fstream.h>
ifstream f("fractii.in");
ofstream g("fractii.out");
long a[1000000];
int main(){
int nr,n,i,j;
f>>n;
for(i=2;i<=n;++i)
a[i]=i-1;
nr=0;
for(i=2;i<=n;++i){
nr+=a[i];
for(j=i*2;j<=n;j+=i)
a[j]-=a[i];
}
nr=2*nr+1;
g<<nr;
return 0;
}