#include <fstream>
using namespace std;

bool s[1000000];

bool prim(int x) {
    if (x%2==0 && x>2) return false;
    else
        for (int d = 3; d*d <= x; d=d+2)
            if (x%d==0)
                return false;
    return true;
}

int main() {
    int n;
    long long p;
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    fin >> n;
    p = n*(n-1)+1;
    for (int i = 2; i <= n/2 ; ++i) {
        if (prim(i)) {
            int nr = n/i-1;
            p -= 2*(nr+(nr*(nr-1)/2));
        }
    }
    fout << p;
    return 0;
}