#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;     
   }