#include<stdio.h>
#include<iostream>
using namespace std;
unsigned long long phi[100000000];
int main()
{
    unsigned long long n,nr=0,i,j;
    
    FILE *in = fopen("fractii.in", "r");
    FILE *out = fopen("fractii.out", "w");
    fscanf(in, "%lld", &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);
               
            nr += (2 * phi[i]) - 1;
    }
    
    nr +=  n ;

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