#include<fstream>
using namespace std;
long long max1=0;
int n,i,j,nr[1000001];
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    for(i=2;i<=n;i++)
        nr[i]=i-1;
    for(i=2;i<=n;i++)
    {
        max1+=nr[i];
        for(j=i+i;j<=n;j=j+i)
            nr[j]-=nr[i];
    }
    max1=max1*2+1;
    g<<max1;
    return 0;
}