#define nmax 1000000
#define _CRT_SECURE_NO_WARNINGS
#include<cstdio>
#include<math.h>

int n;
int v[nmax];

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