#include <fstream>
#include <bitset>

using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

bitset<1000002> p;

int eul[1000001], i, n, j, fr;
int putere(int x, int y) {
    if(y < 0) x = 1/x, y = -y;
    else if(y == 0) return 1;
    else {
        int k = 1;
        while(y > 1) {
            if(y%2 ==0) {
                x = x*x;
                y = y/2;
            } else {
                k = x*k;
                x = x*x;
                y = (y-1)/2;
            }
        }
        return x*k;
    }
}

void euler() {
    eul[1] = 1; eul[2] = 1; eul[3] = 2;
    for(int m = 3; m <= n; m++) {
        int x = m;

        if(x == 1) eul[x] = 1;
        else if(p.test(x) == 0) eul[x] = x-1;
        else {
            int d = 2, p = 0, e = 1;
            while(x > 1) {
                p = 0;
                while(x%d==0) {
                    x = x/d;
                    p++;
                }

                if(p!=0) e = e*(d-1)*putere(d, p-1);
                d++;
            }
            eul[m] = e;
        }
        fr += eul[m];
    }
}

int main()
{
    in >> n;
    p.set(1, 1);
    for(i = 2; i*i <= n; i++) {
        if(p.test(i) == 0) for(j = i*i; j <= n; j = j+i) p.set(j, 1);
    }

    euler();
    fr = fr*2 + 3;
    out << fr;
    return 0;
}