#include <stdio.h>

int main()
{
	 freopen ("fractii.in","r",stdin);
	freopen ("fractii.out","w",stdout);

	int N, i, j;
	scanf("%d", &N);
	int phi[N + 1];
	int count = 0;
	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);
			}
    for(i = 2; i <= N; i++){
    	count += phi[i];
    }
	printf("%d\n", count * 2 + 1);
	return 0;
}