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

import java.util.*;
public class Main {
    public static void main(String[] args){
        System.out.println("Please Enter Your Value");
        Scanner numberInput = new Scanner(System.in);
        long n = numberInput.nextInt();
        long finVal = 0;
        for(int i = 1; i <= n; i++){
        finVal += i;
        }
        System.out.println(finVal);
    }
}