#include <cstdio>
using namespace std;
const int NMAX = 1000005;
int v[NMAX];

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