#include <fstream>
using namespace std;
int a[1000001];

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

int main()
{
    int n, i, j;
    unsigned long long suma=0;
    f>>n;
    for(i=2; i<=n; i++) a[i]=i-1;
    for(i=2; i<=n; i++)
    {
        suma+=a[i];
        for(j=i+i; j<=n; j+=i) a[j]-=a[i];
    }
    g<<suma*2+1<<'\n';
    return 0;
}