declare function local:build-cells($x, $y)
{
    for $num in 1 to fn:count($x)
    return
        [$x[$num] , $y[$num]]
};

declare function local:build-grid($x, $y) {
   (local:build-cells($x, $y),
    local:build-cells($y, $x),
    local:build-cells($x, $y),
    local:build-cells($y, $x),
    if ($x = [1, 1] and $y = [1, 0])
    then
        ()
    else
        local:build-grid(
        ($x ! (. - 1))[position() = 1 to (($x[1] - 1) * 2)],
        (($y)[position() = 2 to ($y[last()] + $y[1])])
        )
    )
};

let $seq :=
  fn:reverse(local:build-grid((for $i in 1 to 800
  return
      400), (fn:reverse((for $i in 0 to 399
  return
      $i)),
  for $i in 1 to 400
  return
      $i)))
return $seq[361527](1) +  $seq[361527](2)