#include <cstdio>
using namespace std;
long long i,j,n,s,a[1000000];
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%ld",&n);
    s=0;
    for (i = 2; i <= n; ++i) a[i] = i;
    for (i = 2; i <= n; i++) if (a[i] == i)
            for (j = i; j <= n; j += i)
            {
                a[j]/=i;
                a[j]*=(i-1);
            }
    for (i=1; i<=n; i++) s+=a[i];
    printf("%lld\n",s*2+1);
    return 0;
}