#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,i,j,a[1000001],v[1000001];
long long s;
int main ()
{
    f>>n;
    for(i=1;i<=n;++i)
    a[i]=i;
    for(i=2;i<=n;++i)
    if(v[i]==0)
    for(j=i;j<=n;j+=i)
    {
        a[j]*=i-1;
        a[j]/=i;
        v[j]=1;
    }
    for(i=2;i<=n;++i)
    s+=a[i];
    s=s*2+1;
    g<<s<<'\n';
    return 0;
}