#include<stdio.h>  
  long long phi[1000001],i,j,n;  
  int main()  
  {       freopen("fractii.in","r",stdin);  
     freopen("fractii.out","w",stdout);  
     scanf("%lld",&n);  
      for(i=2;i<=n;i++)       phi[i]=i-1;  
      for(i=2;i<=n;i++)  
         for(j=2*i;j<=n;j+=i)    phi[j]-=phi[i];  
      j=0;  
      for(i=2;i<=n;i++) j+=phi[i];  
       printf("%lld",j*2+1);  
           return 0;  
  }