      integer :: n,l
      integer :: azi(200),piAziTrue,eat,absMin
      
      read*,n,l
      
      do i = 1,n
        azi(i) = l + i - 1
      end do
      
      piAziTrue = sum(azi(1:n))
      
      absMin = maxval( abs(azi(1:n)) )
      do i = 1,n
        if( abs(azi(i))<=absMin )then
          absMin = abs(azi(i))
          eat = azi(i)
        end if
      end do
      
      print*,piAziTrue - eat
      
      
      end
