#include <fstream>

using namespace std;

long long n,i,j,f[1000010],s;

ifstream fin ("fractii.in");

ofstream fout ("fractii.out");

int main (){

    fin>>n;
    for (i=1;i<=n;i++)
        f[i] = i;

    for (i=2;i<=n;i++){
        if (f[i] == i)
            for (j=i;j<=n;j+=i)
                f[j] = f[j]/i*(i-1);
    }
    for (i=2;i<=n;i++)
        s+=f[i];
    fout<<s*2+1;


    return 0;
}