#include <iostream>
#include <fstream>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int v[1000001];

int main()
{
    int N, i, j;
    long long Sol = 0;
    f >> N;
    for(i = 2; i <= N; i++)
        v[i] = i;
    for(i = 2; i <= N; i++)
    {
        if(v[i] == i)
            for(j = i; j <= N; j += i)
                v[j] = v[j] / i * (i - 1);
        Sol += v[i];
    }
    g << 2 * Sol + 1;
    f.close();
    g.close();
    return 0;
}