import java.util.Scanner;public class Main {    public static void main(String[] args) {                    Scanner scanner= new Scanner(System.in);            int sum,n;            while(scanner.hasNext())            {                 n=scanner.nextInt();                 sum=0;                for(int i=1;i<=n;i++)                {                    sum+=i;                }                System.out.println(sum);                System.out.println();                        }            scanner.close();                }}