#include<cstdio>
#define Nmax 1000003
#define I64 long long
using namespace std;

long a[Nmax];
I64 rez;
int main()
{
    long i,n,j;
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%ld",&n);
    for(i=1;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]=a[j]/i*(i-1);
    for(i=2;i<=n;++i)
    rez=rez+a[i];
    printf("%I64d\n",2*rez+1);
    return 0;
}