#include <iostream>
#include <fstream>

using namespace std;

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

long long i, j, N, s = 0;
long long cartofi[1000000];

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