#include <fstream>
using namespace std;
int s[1000001],n,i,j;
unsigned long long r;
ifstream f("fractii.in");
ofstream g("fractii.out");
int main()
{
f>>n;
for(i=2;i<=n;i++)
s[i]=i-1;
for(i=2;i<=n;i++)
{
r+=s[i];
for(j=i+i;j<=n;j=j+i)
s[j]-=s[i];
}
r*=2;
g<<r+1;
}