#include <fstream>
#define Nmax 1000099
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");

int n,v[Nmax];

int main()
{
    f>>n;
    for(int i=1;i<=n;i++)v[i]=i-1;
    unsigned long long S=0;
    for(int i=2;i<=n;i++)
    {
        int aux=v[i];
        S+=aux;
        for(int j=2*i;j<=n;j+=i)v[j]-=aux;
    }
    g<<2*S+1<<'\n';
    f.close();g.close();
    return 0;
}