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

    public static void main(String[] args){
           Scanner kb = new Scanner(System.in);
           System.out.println("Enter an integer");
           int num = kb.nextInt();
           kb.close();
           System.out.println(
                IntStream.rangeClosed(1, num).reduce(0, (x, y) -> x + y)
           );
           
    }
}