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