#include<cstdio>
using namespace std;
int i,j,n,v[1000001];
long long s=0;
FILE *f1,*f2;
int main()
{
    f1=freopen("fractii.in","r",stdin);
    scanf("%d",&n);
    fclose(f1);
    for(i=1;i<=n;i=i+1)
    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=1;i<=n;i++)
    s=s+v[i];
    s=2*s-1;
    f2=freopen("fractii.out","w",stdout);
    printf("%lld\n",s);
    fclose(f2);
    return 0;
}