#include <fstream>
#include <vector>
#include <numeric>
#include <utility>
#include <iostream>

using std::cout;
using std::ifstream;
using std::ofstream;
using std::accumulate;
using std::vector;

int main(){
    ifstream f("fractii.in" );
    ofstream g("fractii.out");
    int N = 0;
    f>>N;
    vector<int> phi(N+1,0);
    for(int i = 1;i<=N;i++){
        phi[i] = i;
    }
    long long counter = 0;
    for(int i = 1;i<=N;i++){
        counter += phi[i];
        for(int j = 2;i*j <= N;j++){
            phi[i*j] -= phi[i];
        }
    }
    g<<2*counter -1;
    return 0;
}