#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int n,i,j,phi[1000010];
long long sol;
int main() {
    fin>>n;
    //phi[i]=numarul numerelor prime mai mici decat i(indicatorul lui euler)
    for (i=1;i<=n;i++)
        phi[i]=i-1;
    for (i=2;i<=n;i++)
        for (j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
    for (i=2;i<=n;i++)
        sol+=1LL*phi[i];
    fout<<1+2*sol;
    return 0;
}