#include <cstdio>
using namespace std;
int a[1000005];
long long ans;
int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    int n; scanf("%d", &n);
    for (int i = 2; i <= n; ++i)
        a[i] = i - 1;
    for (int i = 2; i <= n; ++i)
    {
        for (int j = i + i; j <= n; j += i)
            a[j] -= a[i];
        ans += 1LL * 2 * a[i];
    }
    printf("%lld\n", ans + 1);
    return 0;
}