#include <cstdio>
using namespace std;

long long max=0;
long long v[1000001], n, i, j;

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