#include <fstream>
using namespace std;
const int maxn = 1000010;


    long unsigned phi[maxn];
    int n;
void ciur()
{
    int i,j;
    for(i=2;i<=n;++i)
        phi[i] = i;
    for(i=2;i<=n;++i)
    {
        if(phi[i] == i)
            for(j=i;j<=n;j+=i)
                phi[j] = (long long)phi[j] * (i-1)  / i;
    }
}

int main()
{
    ifstream in("fractii.in");
    ofstream out("fractii.out");
    in >> n;
    ciur();
    int i;
    long long sol = 0;
    for(i=2;i<=n;++i)
        sol += phi[i] *2;
    out << (sol+1);
    return 0;
}