program yukicoder_4
  use, intrinsic :: iso_fortran_env
  implicit none
  integer(int32) :: n, sum_w
  integer(int32), allocatable :: ws(:)
  logical, allocatable :: dp(:, :)
  integer(int32) :: i, j, bef
  read(input_unit, *) n
  allocate(ws(n))
  read(input_unit, *) ws(:)
  sum_w = sum(ws(:))
  if (iand(sum_w, b'1') == 1) then
     write(output_unit, '(a)') "impossible"
     stop
  end if
  !> sum_w is even.
  allocate(dp(0:sum_w / 2, 0:n), source = .false.)
  dp(0, 0) = .true.
  do i = 1, n
     dp(:, i) = dp(:, i - 1)
     do j = 0, sum_w / 2
        bef = j - ws(i)
        if (bef < 0) cycle
        !> bef >= 0
        if (.not. dp(bef, i - 1)) cycle
        dp(j, i) = .true.
     end do
  end do
  write(output_unit, '(a)') trim(merge("possible  ", "impossible", dp(sum_w / 2, n)))
end program yukicoder_4