using System;

public class Program

{

    //Bài 1: Tính S(n) = 1 + 2 + 3 + … + n

    public static void Main(String [] args){

        Console.WriteLine("Please enter ur n");

        int n= int.Parse(Console.ReadLine());

        sumN(n);

    }

    public static void sumN(int n){

        int rs = 0;

        for(int i=1;i<=n;i++){

            rs +=i;

        }

        Console.WriteLine("Result: "+rs);

    }

}