#include <bits/stdc++.h>

using namespace std;

int p[1000005];

int main()
{
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);

    int n;
    cin >> n;
    for(int i = 1; i <= n; i ++)
        p[i] = i;
    for(int i = 2; i <= n; i ++) {
        if(p[i] == i) {
            for(int j = 1; j <= n / i; j ++) {
                p[i * j] /= i, p[i * j] *= (i - 1);
            }
        }
    }
    long long ret = 0;
    for(int i = 1; i <= n; i ++) {
        ret += p[i];
    }
    cout << ret * 2 - 1 << "\n";

    return 0;
}