# include <cstdio>
# include <stdlib.h>

using namespace std;

int phi[1000005];
long long n,ct;
void ciur()
{int i,j;
     for (int 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];
}
int main()
{int i;
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    
    ciur();
    scanf("%lld",&n);
    
    for (i = 2; i <= n; i++)
    ct += phi[i];
    
    ct *= 2;
    ct++;  
    
    printf("%lld",ct);

return 0;
}