#include <fstream>
#include <cstring>

using namespace std;

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

int phi[1000001];

int main()
{
    unsigned long long n,s=0;
    fin>>n;
    for(int i=1;i<=n;i++)
        phi[i] = i;
    for(int i=2;i<=n;i++)
    {
        if(phi[i]==i)
            for(int j=i;j<=n;j+=i)
            {
                phi[j]/=i;
                phi[j]*=i-1;
            }
        s+=phi[i];
    }
    fout<<2*s+1<<'\n';
    fin.close();
    fout.close();
    return 0;
}