#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int phi[1000001];
int main()
{
    int n,i,j;
    long long s=1;
    f>>n;
    for(i=1;i<=n;i++)
        phi[i]=i-1;
    for(i=2;i<=n;i++)
        for(j=2*i;j<=n;j+=i)
        phi[j]=phi[j]-phi[i];
    for(i=1;i<=n;i++)
        s=s+2*phi[i];
    g<<s;
    return 0;
}