#include<stdio.h>
#include<iostream>
using namespace std;
int main()
{
    unsigned long long n,nr=0,i,j;
    unsigned long long phi[1000000];
    FILE *in = fopen("fractii.in", "r");
    FILE *out = fopen("fractii.out", "w");
    fscanf(in, "%lld", &n);
    
    for(int i=1;i<=n;i++)
            phi[i] = i-1;
    
    
    
    for(int i=2;i<=n;++i)
    {
            for(int j=2*i;j<=n;j +=i)
                    phi[j] -= phi[i];
                    
            nr += phi[i];
            
            if(i>=3)
             nr += phi[i]-1;  
    }
    
    //for(int i=1;i<=n;i++)
    //     nr += phi[i];
    nr +=  n ;
    /*if(nr >= 3)
          for(i=3;i<=n;i++)
             nr += phi[i]-1;  */
    //cout<<phi[4];

    fprintf(out,"%lld", nr);
    
    
}