#include <stdio.h>

long long v[1000001];
long long i,n,j,s;

int main ()
{
    freopen ("fractii.in","r",stdin);
    freopen ("fractii.out","w",stdout);
    
    scanf ("%lld",&n);
    
    for (i=2;i<=n;i++) v[i]=i;
    
    for (i=2;i<=n;i++){
        if (v[i]==i) for (j=i;j<=n;j=j+i) v[j]=v[j]/i*(i-1);
        }
        
    for (i=2;i<=n;i++) s=s+v[i];
    
    printf ("%lld\n",1LL*s*2+1);
    
    return 0;
}