#include<stdio.h>
FILE *f=fopen("fractii.in","r"),
     *g=fopen("fractii.out","w");
int i,j,n;
long long s,ni[1000006],nu[1000006],cal;
int main()
{ fscanf(f,"%d",&n);
  for(i=2;i<=n;++i) if(nu[i]==0){ for(j=i;j<=n;j+=i) { if(ni[j]==0) ni[j]=1;
						       if(nu[j]==0) nu[j]=1;
						       ni[j]*=i;
						       nu[j]*=i-1;
						     }
				}
  s=n;
  for(i=2;i<=n;++i) { cal=n*nu[i];
		      if(cal%ni[i]) ++s;
		      cal/=ni[i];
		      s+=cal;
		    }
  fprintf(g,"%lld\n",s);
  fclose(f);
  fclose(g);
  return 0;
}
//41