#include <fstream>
#include <iostream>
using namespace std;

int p[1000001];

int main() {
    int n, i, j;
    long long rez = 0;
    ifstream f("fractii.in");
    f >> n;
    f.close();
    for (i = 1; i <= n; i++)
        p[i] = i;
    for (i = 2; i <= n; i++)
        if (p[i] == i) {
            p[i]--;
            for (j = 2; j * i <= n; j++)
                p[i * j] = p[i * j] / i * (i - 1);
        }
    for (i = 1; i <= n; i++)
        rez += p[i];
    ofstream g("fractii.out");
    g << 2 * rez - 1;
    g.close();
    return 0;
}