/**
 * Created by iyasuwatts on 10/17/17.
 */

import java.util.Scanner;
public class Main {

    public static void main(String[] args){
        
        Scanner input = new Scanner(System.in);
        System.out.println( "Give Ending Value:");
        
        int num = input.nextInt();
        int result = 0;
        
        for( int i = 1; i <= num; i++){
            result += i;
        }
        
        System.out.println(result);
}
}