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