#include<stdio.h>
#include<stdlib.h>
long n,phi[1000001],i,j;
long double s;
int main()
  {
   freopen("fractii.in","rt",stdin);
   freopen("fractii.out","wt",stdout);
   scanf("%ld",&n);
   for(i=1;i<=n;++i) phi[i]=i;
   for(i=2;i<=n;++i)
      {if(phi[i]==i)
          for(j=i;j<=n;j+=i)
             phi[j]/=i,phi[j]*=(i-1);
      s+=phi[i];
      }
   printf("%.Lf",2*s+1);
   //system("PAUSE");
   return 0;
  }