#include <fstream>
using namespace std;
long long n,i,j,v[1000010],s;
ifstream f ("fractii.in");
ofstream g ("fractii.out");
int main (){

    f>>n;
    for (i=1;i<=n;i++)
        v[i] = i;
    for (i=2;i<=n;i++){
        if (v[i] == i)
            for(j=i;j<=n;j+=i)
               v[j]=v[j]/i*(i-1);
    }
    for (i=2;i<=n;i++)
        s+=v[i];
    g<<s*2+1;
    return 0;
}