#include <cstdio>

#define FILEIN "fractii.in"
#define FILEOUT "fractii.out"

using namespace std;

const int NMAX = 1000002;

int phi[NMAX];

int main()
{
    int n, i, j;
    freopen(FILEIN, "r", stdin);
    freopen(FILEOUT, "w", stdout);
    scanf("%d", &n);

    phi[1] = 1;
    for ( i = 2; i <= n; i++) {
        phi[i] = i-1;
    }

    for ( i = 2; i <= n; i++) {
        for ( j = i*2; j <= n; j += i) {
                phi[j] -= phi[i];
        }
    }

    long long int sol = 0;
    for ( i = 2; i <= n; i++) {
        sol += phi[i];
    }

    printf("%lld\n", (long long int)(sol * 2 + 1));

    return 0;
}