#include<stdio.h>
#include<stdlib.h>
long long int v[1000000],n,nr;
int main()
{FILE *fo=fopen("fractii.in","r"),*fc=fopen("fractii.out","w");
 fscanf(fo,"%d",&n);
 fclose(fo);
 for(int i=1;i<=n;i++)
    v[i]=i;
 for(int i=2;i<=n;i++)
  if(v[i]==i)
	 for(int j=i;j<=n;j+=i)
		{v[j]/=i;
         v[j]*=(i-1);
        }
 for(int i=1;i<=n;i++)
   nr+=v[i];
 fprintf(fc,"%lld",2*nr-1);
 fclose(fc);
 return 0;
}