#include <bits/stdc++.h>
#define NMAX 1000010
#define ll long long
using namespace std;
ifstream in("functii.in");ofstream out("functii.out");
ll N,v[NMAX],S;
int main()
{
    in >> N;
    for(int i = 1; i <= N; ++i)
        v[i] = i;

    for(int i = 1; i <= N; ++i)
    {
        if(v[i] == i)
            for(int j = i; j <= N; j+=i)
                v[j] = v[j] / i*(i-1);

        S+=v[i];

    }


    out << S*2 + 1;
    out.close();

    return 0;
}