#include <stdio.h>   
  
long long i,j,sum,n;   
long long phi[1000010];   
  
int main()   
{   
    freopen("fractii.in","r",stdin);   
    freopen("fractii.out","w",stdout);   
       
    scanf("%lld",&n);   
       
    for (i=1; 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];   
        sum+=phi[i];   
    }   
    sum=sum*2+1;   
       
    printf("%lld\n",sum);   
       
    return 0;   
}