#include <bits/stdc++.h>

using namespace std;

ifstream fin  ("fractii.in");
ofstream fout ("fractii.out");

long long phi(long long x){
    long long answer = x;

    for(long long i=2; i<=x/i; i++)
        if(x%i == 0){
            answer -= answer / i;
            while(x%i == 0)
                x /= i;
        }
    if(x > 1)
        answer -= answer / x;

    return answer;
}

signed main (){
    ios_base::sync_with_stdio(false);
    fin.tie(nullptr);
    fout.tie(nullptr);

    long long n, sol = 1;
    fin>>n;
    for(long long i=2; i<=n; i++)
        sol += 2 * phi(i);
    fout<<sol;
    return 0;
}