#include<stdio.h>
#include<stdlib.h>
int n,phi[1000002];
int main()
  {int i,j,s=0;
   freopen("fractii.in","rt",stdin);
   freopen("fractii.out","wt",stdout);
   scanf("%d",&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);
   for(i=2;i<=n;++i) s+=phi[i];
   printf("%d",2*s+1);
   //system("PAUSE");
   return 0;
  }