import java.util.ArrayList;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {


        Scanner tamere = new Scanner(System.in);
        int rigoloNombre = tamere.nextInt();

        int resultons = recurenceDuGhetto.testonsCa(rigoloNombre);


        System.out.println(resultons);

    }


}

























public class recurenceDuGhetto {

    public recurenceDuGhetto() {

    }

    public static int testonsCa(int n) {
        if (n == 0 || n == 1) {
            return 1;
        }
        if (n == 2)
            return 2;
        if (n == 3)
            return 5;
        else{
            int resultat = 1;

            for (int i = 1; i < n; i++){
                int extra = (n - i) * testonsCa(i);
                resultat = resultat + extra;
                //System.out.println(i + " i bah il vaut et extra il vaut " + extra + " et enfin result " + resultat);
            }
            return resultat;
        }

    }
}