#include<fstream>
#define MAX 1000005
using namespace std;

int x[MAX],n;
long nr=1;

int main(){
    ifstream in("fractii.in");
    in>>n;
    for(int i=2;i<=n;++i)
        x[i] = i-1;
    for(int i=2;i<=n;++i)
        {
        nr += 2*x[i];
        for(int j=2*i;j<=n;j+=i)
            x[j] -= x[i];
        }
    ofstream out("fractii.out");
    out<<nr;
    in.close();
    out.close();
    return 0;
}