using System;

public class Program

{

    public static void Main()

    {

        int c,t,n=0;

        c=Convert.ToInt32(Console.ReadLine());

        t=Convert.ToInt32(Console.ReadLine());

            if(c<t)

            {

                if(c%2==0)

                    c=c+1;

                do

                {

                    n=n+c;

                    c=c+2;

                }

                while(c<=t);

                    Console.WriteLine(n);

            }

        else

        {

            if(c%2==0)

                c=c-1;

            do

            {

                n=n+c;

                c=c-2;

            }

            while(c>=t);

                Console.WriteLine(n);

        }

    }

}

​

​

​

#add all the evevn number s-b,b-s using do while loop:

​

​

​

using System;

public class Program

{

    public static void Main()

    {

        int c,t,n=0;

        c=Convert.ToInt32(Console.ReadLine());

        t=Convert.ToInt32(Console.ReadLine());

            if(c<t)

            {

                if(c%2==1)

                    c=c+1;

                do

                {

                    n=n+c;

                    c=c+2;

                }

                while(c<=t);

                    Console.WriteLine(n);

            }

        else

        {

            if(c%2==1)

                c=c-1;

            do

            {

                n=n+c;

                c=c-2;

            }

            while(c>=t);

                Console.WriteLine(n);

        }

    }

}