program main

  implicit none
  integer(8) :: h, w
  integer(8) :: i, j, k

  
  read(*,*) h, w

  if( mod(h,2) == 0 ) then 
    i = h/2 
    j = w 
    k = i*j
  else
    i = h/2 + 1 
    j = w
    k = i*j - w/2
  end if
  if( h == 1 .or. w == 1 )then 
    print*, 1
  else
    print*, k
  end if
  

end program main
