#include<stdio.h>
int a[1100000];
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    int i,n,j;
    long long t=0;
    scanf("%d",&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=1;i<=n;i++)
        t+=a[i];
    t*=2;
    t--;
    printf("%lld",t);
    return 0;
}