#include<fstream.h>
 ifstream f("fractii.in");
  ofstream g("fractii.out");
   long v[1000001];
   long n;
   long long i,j,s=0;
   int main(){
       f>>n;
       for(i=2;i<=n;i++) v[i]=i-1;
       for(i=2;i<=n;i++){s+=v[i];
           for(j=i*2;j<=n;j+=i)
               v[j]=v[j]-v[i];
       }
       s=s*2+1;
       g<<s<<"\n";
       g.close();
       return 0;
   }