#include <fstream>

using namespace std;

ifstream in ("fractii.in");
ofstream out ("fractii.out");

const int N = 1000005;

int e[N];
long long sol = 1;

int main()
{
    int n;
    
    in >> n;
    
    for(int i=1;i<=n;i++)
        e[i] = i;
    for(int i=2;i<=n;i++) {
        if(e[i] == i)
            for(int j=i;j<=n;j+=i)
                e[j] = e[j]/i * (i-1);
        sol+=2*e[i];
    }
    
    out << sol << "\n";
    
    return 0;
}