#include <fstream>
#define DIM 1000002

using namespace std;

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

int N,F[DIM];
long long S;
int main(){
    fin>>N;
    for(int i=2;i<=N;i++)
        F[i]=i;
    for(int i=2;i<=N;i++)
        if(F[i]==i)
        for(int j=i;j<=N;j+=i)
            F[j]=F[j]/i*(i-1);
    for(int i=2;i<=N;i++)
        S+=F[i];
    fout<<2*S+1<<"\n";
    fin.close();fout.close();
    return 0;
}