import java.util.Scanner;

/**
 * Created by iyasuwatts on 10/17/17.
 */
public class Main {

    public static void main(String[] args){
        Scanner keyboard = new Scanner(System.in);
        System.out.println("Enter a valid integer number.");
        int n = keyboard.nextInt();
        
        int sum = 0;
        for(int i = 1; i <= n; i++)
        {
            sum += i;
        }
        
        System.out.println("The sum of the numbers 1 to " + n + " is " + sum);
    }
}