#include <bits/stdc++.h>
#define cin ci
#define cout co
#define int long long
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int n;
vector<int> phi;
void euler()
{
    for(int i = 2; i <= n; i ++)
        phi[i] = i;
    for(int i = 2; i <= n; i ++)
        if(phi[i] == i)
            for(int j = i; j <= n; j += i)
                phi[j] -= phi[j] / i;
}
int32_t main()
{
    cin >> n;
    phi.resize(n + 5);
    euler();
    int ans = 0;
    for(int i = 2; i <= n; i ++)
        ans += 2 * phi[i];
    ans ++;
    cout << ans;
    return 0;
}