#include<stdio.h>
int v[1000001];

int main(){
	long N, nr = 0, i, j;
	

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

	scanf("%ld", &N);

	for(i = 2; i <= N; ++i )
		v[i] = i - 1;
	for(i = 2; i <= N; ++i)
		for( j = 2; i * j <= N; ++j)
			v[i*j] -= v[i];

	for(i = 2; i <= N; ++i)
		nr += v[i];

	nr = 2 * nr + 1;
	printf("%ld", nr);

	return 0;
}