#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");
    
int main() { 
    int v[1000001], n;
    
    while (fin >> n) {
        for (int i = 1; i <= n; i++) {
            v[i] = i;
        }
        
        for (int i = 2; i <= n; i++) {
            if (v[i] == i) {      
                v[i]--;           
                for (int j = i * 2; j <= n; j += i) {
                    v[j] = v[j] / i * (i - 1);
                }
            }
        }

        long long int ans = 1; 

        for (int i = 2; i <= n; i++) {
            ans = ans + 2 * v[i]; 
        }
        
        fout << ans << " ";
    }

    return 0;
}