using System;

namespace Example20
{
	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class Class1
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			Console.Write("Input the upper bound: ");
			int N = int.Parse(Console.ReadLine());

			Console.Write("The sum of the 1st {0} positive integers is ", N);

			int sum = 0;
			
			for (int i = 0; i <= N; i++)
			{
				sum = sum + i;
			}

			Console.WriteLine(sum);
		}
	}
}