#include <cstdio>
using namespace std;

int n, p[1000005];
int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    scanf("%d", &n);
    long long Sol = 1;
    for(int i = 2; i <= n ; ++i){
        p[i] += i - 1;
        for(int j = i * 2; j <= n ; j += i)
            p[j] -= p[i];
        Sol = Sol + p[i] * 2;
    }
    printf("%lld", Sol);
    return 0;
}