#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int a[1000001],n;long long s;
int main()
{
    f>>n;
    for(int i=1;i<=n;++i)
        a[i]=i-1;
    for(int i=2;i<=n;i++)
        for(int j=2*i;j<=n;j+=i)
            a[j]-=a[i];
    for(int i=2;i<=n;i++)
        s+=a[i];
    g<<2*s+1<<'\n';
    return 0;
}