#include <fstream>

using namespace std;
int a[1000005],n;

 void Phi(int n)
{
    int i,j;
    for(i=2;i<=n;i++)
        a[i]=i-1;
    for(i=2;i<=n;i++)
        for(j=i+i;j<=n;j=j+i)
            a[j] = a[j] - a[i];
}
int main()
{
    int i;long long S;
    Phi(1000000);
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    fin>>n;
    S=1;
    for(i=2;i<=n;i++)
        S=S+2*a[i];
    fout<<S<<"\n";
    fin.close();
    fout.close();
    return 0;
}