#include<fstream>
#define maxn 1000010
using namespace std;

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

long long phi[maxn];
int N;

void calculatePhi() {
    for(int i = 1; i <= N; i++)
        phi[i] = i * 1LL;

    for(int i = 2; i <= N; i++) {
        if(phi[i] == i)
            for(int j = i; j <= N; j += i) {
                phi[j] /= i;
                phi[j] *= (i-1);
            }
    }
}

int main() {
    in>>N;
    long long result = 1LL;
    calculatePhi();
    for(int i = 2; i <= N; i++)
        result += phi[i];
    result *= 2LL;
    result -= 1LL;
    out<<result;
}