program yukicoder_2854
  use, intrinsic :: iso_fortran_env
  implicit none
  integer(int64), parameter :: infini = ishft(1_int64, 55)
  integer(int32) :: n
  integer(int64), allocatable :: arr(:), dp(:, :)
  integer(int32) :: i
  read(input_unit, *) n
  allocate(arr(n))
  read(input_unit, *) arr(:)
  allocate(dp(-1:1, 0:n), source = -infini)
  dp(-1, :) = 0_int64
  do i = 1, n
     !> 今の長さが偶数(0).
     dp(0, i) = max(dp(0, i - 1), dp(1, i - 1) + arr(i))
     !> 今の長さが奇数(1).
     dp(1, i) = max(dp(1, i - 1), dp(0, i - 1) - arr(i), dp(-1, i - 1) - arr(i))
  end do
  ! do i = 1, n
  !    write(error_unit, '(*(g0, 1x))') i, ":", dp(:, i)
  ! end do
  write(output_unit, '(i0)') maxval(dp(0:1, n))
end program yukicoder_2854