#include <bits/stdc++.h>

using namespace std;

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

static inline void Phi(int n) {
    for(int i = 1; i <= n; i++) phi[i] = i;
    for(int i = 2; i <= n; i++) {
        if(phi[i] == i) {
            phi[i]--;
            for(int j = 2 * i; j <= n; j += i) phi[j] = phi[j] / i * (i - 1);
        }
        r += phi[i];
    }
}

int main() {
    fin >> n;
    Phi(n);
    fout << 2 * r + 1;

    return 0;
}