#include <bits/stdc++.h>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n, i, j, phi[1000002];
long long rasp;

int main() {
    fin >> n;
    for(i = 1; i <= n; i++) phi[i] = i;
    for(i = 2; i <= n; i++) {
        if(phi[i] == i) {
            for(j = i; j <= n; j += i) {
                phi[j] = phi[j] / i * (i - 1);
            }
        }
        rasp += phi[i];
    }
    fout << 2 * rasp + 1;

    return 0;
}