#include<fstream>
#define ll long long
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
const int Nmax = 1000001;
int E[Nmax];
int N;
int main(){
    in>>N;
    for(int i=1;i<=N;i++) E[i]=i;
    for(int i=2;i<=N;i++){
        if(E[i]==i){
            for(int j=i;j<=N;j+=i){
                E[j]=E[j]/i*(i-1);
            }
        }
    }
    ll s=0;
    for(int i=1;i<=N;i++) s+=E[i];
    out<<2*s-1<<'\n';
    return 0;
}