#include <fstream.h>
ifstream f("fractii.in");
ofstream g("fractii.out");
long long r;
int n,i,j,a,x[1000001];
int main()
{
    f>>n;
    for(i=2;i<=n;i++) x[i]=i-1;
       for(i=2;i<=n;i++) { r=r+x[i];
                           for(j=i+i;j<=n;j+=i) x[j]-=x[i];
                          }
    r*=2;
    r++;
    g<<r<<"\n";
    f.close();
    g.close();
    return 0;
}