using System;

public class Program

{

    public static void Main()

    {

        int N=Int32.Parse(Console.ReadLine());

        int opt=Int32.Parse(Console.ReadLine());

        int sum=0;

 sum+=N;

 N=N-1;

 if(opt==2)

 {

 if(N%2==0)

{

 while(N>0)

 {

 if(N%2==0)

 sum+=N;

 else

 sum-=N;

 N--;

 }

 }

else

{

 while(N>0)

 {

 if(N%2==0)

 sum-=N;

 else

 sum+=N;

 N--;

 }

 }

 }

 else

 {

 if(N%2==0)

{

 while(N>0)

 {

 if(N%2==0)

 sum-=N;

 else

 sum+=N;

 N--;

 }

 }

 else

{

 while(N>0)

 {

 if(N%2==0)

 sum+=N;

 else

 sum-=N;

 N--;

 }

 }

 }

 Console.WriteLine(sum);

    }

}