package b558; import java.util.ArrayList; import java.util.Scanner; public class b558 { public static void main(String[] args) { // TODO Auto-generated method stub Scanner scanner = new Scanner(System.in); ArrayList list = new ArrayList<>(); list.add(1); for(int i = 0 ; i <=500; i ++) { list.add(list.get(i)+i+1); } while (scanner.hasNext()) { System.out.println(list.get(scanner.nextInt()-1)); } } }