#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int  v[1000003];
int main()
{
	long n, i, j;
	long long s=0;
    in >> n;
    for(i=1;i<=n;i++) 
		v[i]=i;
    for(i=2;i<=n;i++)
        if(v[i]==i)               
            for(j=i;j<=n;j=i+j)  
                v[j]=v[j]/i*(i-1);
    for(i=1;i<=n;i++)  
		s+=v[i];
    out << 2*s-1 ;
    in.close();
	out.close();
    return 0;
}