import java.util.Scanner;

public class SpaceSplit {

public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc=new Scanner(System.in);
while(sc.hasNext()){
int n=sc.nextInt();
int out=(int) ((Math.pow(n, 3)+5*n)/6+1);
System.out.println(out);

}
}

}