using System;

public class Program

{

    public static void Main()

    {

        int  min , max , tmp , sum;

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

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

        if ( min > max )

        {

            tmp = min;

            min = max;

            max = tmp;

        }

        sum = 0;

        for (int i = min ; i <= max ; i++)

        {

            sum = sum +i;

        }

        Console.WriteLine(sum);

        Console.ReadLine();

    }

}