#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n, phi[1000010];
long long int a;
int main() {
    fin>>n;
    for (int i=2;i<=n;i++)
        phi[i]=i-1;
    for (int i=2;i<=n;i++) {
        a+=phi[i];
        for (int j=2*i;j<=n;j+= i)
            phi[j]-=phi[i];
    }
    fout<<2 *a+1<<'\n';
    return 0;
}

// phi 4= 4(2-1)/2;  3-