/**
 * Created by iyasuwatts on 10/17/17.
 */
import java.util.*;
public class Main {

    public static void main(String[] args){
        
        int x, y, sum = 1;
        Scanner sc = new Scanner(System.in);
        System.out.println("Input a number below!!");
        x = sc.nextInt();
        
        for (y = 1; y <= x; y++){
            sum += y;
        }        

        System.out.println("The sum is "+ sum);
                

    }
}