using System;
using System.Collections.Generic;
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
#if LocalDebug
            var exStdIn = new System.IO.StreamReader("stdin.txt");
            System.Console.SetIn(exStdIn);
#endif
            var N = GetData();
            var Sum = 0;

            for (int i = 1; i <= N; i++)
            {
                Sum += i;
            }

            System.Console.WriteLine(Sum);
#if LocalDebug
            System.Console.ReadKey();
#endif
        }

        static int GetData()
        {
            return int.Parse(Console.ReadLine());
        }



    }
}