#include <bits/stdc++.h>
using namespace std;
ifstream f ("fractii.in");
ofstream g ("fractii.out");
const int M = 1e6 + 1;
int main() {
    int a[M], n;
    unsigned long long s = 0;
    f >> n;
    for (int i = 2; i <= n; i ++) a[i] = i;
    for (int i = 2; i <= n; i ++) if (a[i] == i) {a[i] --; for (int j = 2 * i; j <= n; j += i) a[j] = a[j] / i * (i - 1);}
    for (int i = 2; i <= n; i ++) s += a[i];
    s *= 2; s ++;
    g << s;
    return 0;
}