#include <fstream>

using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int main()
{
    long long n , i ,j ,e[1000001],s=0;
    in >> n;
    for(i=1;i<=n;i++)
        e[i]=i;
        for(i=2;i<=n;i++)
            if(e[i]==i)
                for(j=i;j<=n;j+=i)
                    e[j]=e[j]/i*(i-1);
    for(i=1;i<=n;i++){
    s+=e[i];
    }
    out << 2*s-1;
    return 0;
}