#include <iostream>
#include <fstream>

int fi[1000005];
using namespace std;

int main ()
{
    int n,s;
    ifstream fin ("fractii.in");
    ofstream fout ("frcatii.out");
    fin >> n;
    s=1;
    for (int a=2;a<=n;a++){
        fi[a]=a;
    }
    for (int i=2;i<=n;i++){
        if (fi[i]==i){
            for (int j=i;j<=n;j=j+i){
                fi[j]=fi[j]*(i-1)/i;
            }
        }
        s=s+2*fi[i];
    }
    fout << s << endl;


}