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