#include<stdio.h>
long vector[1000100],n,i,j;
long long s;
int main()
{
   freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
   scanf("%ld",&n);
   for(i=1;i<=n;++i)
        vector[i]=i;
   for(i=2;i<=n;++i)
       if(vector[i]==i)
          for(j=i;j<=n;j+=i)
              vector[j]=vector[j]/i*(i-1);
  for(i=2;i<=n;++i)
        s=s+vector[i];
   printf("%lld\n",2*s+1);
   return 0;
}