program sample
    implicit none
  
    integer(8) :: i,j,m,n,h,w
    real(8)::a,b
    integer(8),allocatable :: x(:),y(:)
  
    read(*,*) h,w
    if (h==1 .or. w ==1)then
        write(*,*)1
        stop
    end if
    if (mod(h*w,2)==0)then
        write(*,*) h*w/2
    else
        write(*,*) h*w/2+1
    end if

  
    stop
end program sample
  

