/**
 * Created by iyasuwatts on 10/17/17.
 */
import java.util.Scanner;

public class Main {

    public static int main(int input){
        int numberTotal = 0;
       

        //Scanner sc = new Scanner(System.in);
        //int input = sc.nextInt();
        for (int n = 0 ; n <= input ; n++){
            
            numberTotal += n;
        }
        return numberTotal;

        

    }
}