/**
 * Created by iyasuwatts on 10/17/17.
 */
import java.util.*;
public class Main {
    private static int num;
    
    public Main(int n){
        
    }

    /*public static int getN(){
        return n;
    }
    
    public static void setN(int a){
        n=a;
    }   */
    
    public static void main(String[] args){
        
        //setN(0);
        Scanner input = new Scanner(System.in);
        System.out.println("Please enter a number");
        int num = input.nextInt(); 
        int sum = 0;
        for(int i = num; i>=1; i--){
            sum += i;
        }
        System.out.println("sum of 1 to " + num + " is " + sum);
    }
}