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


#include <fstream>

using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");
int n;
int j;
int v[1000001];
long long s;
int main()
{
 cin >> n;
 int i;
 s = 1;
 for (i = 1 ; i <= n; i ++)
    v[i] = i;
 for (i = 1; i <= n; i ++)
    for (j = i * 2; j <= n; j = j + i)
        v[j] --;
 for (i = 2; i <= n; i ++)
    s = s + 2 * v[i];
 cout << s;
}