#include <cstdio>
using namespace std;
int v[1000001];
 

 
int main(){
	
	freopen("fractii.in", "r", stdin);
	freopen("fractii.out", "w", stdout);
	
    int n, i, j;
    long suma=0;
    scanf("%d", &n);
    
    for(i=2; i<=n; i++) {
    	v[i]=i-1;
	}
	
    for(i=2; i<=n; i++){
        suma=suma+v[i];
        for(j=2*i; j<=n; j=j+i) v[j]=v[j]-v[i];
    }
    
    printf ("%ld\n",suma*2+1 );
    
    return 0;
}