#include <fstream>
using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int n, v[1000002],i,j;
unsigned long long rez;

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

}