#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");

int main() {
    int n, f;
    in >> n;
    f = (2 * n) - 1;
    for (int i = 2; i <= n; i++)
        if (i % 2 == 0) {
            for (int j = 3; j <= n; j+=2)
                f++;
        } else {
            for (int j = 2; j <= n; j+=2)
                f++;
        }
    out << f;
}