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

    public static void main(String[] args){

    }
    
    public void sumNums() {
        Scanner sn = new Scanner(System.in);
        int num = sn.nextInt();
        int sum = 0;
        for(int i = 1; i<=num; i++) {
            sum += i;
        }
        System.out.println(sum);
        
        
    }
}