#include <stdio.h>

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

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