On a farm divided into a grid of cells, every cell either has grass on it or is empty. If two adjacent cells have grass, they will belong to a common field. The common field extends in all directions to all adjacent cells with grass. So, if cell A is adjacent to cell B and cell B is adjacent to cell C, and all three have grass, then they all lie in the same field. If a cell with grass has no adjacent cell with grass, then it will be a field 1-cell field. Every field must feed one sheep or one cow. Each field of grass cannot be shared between cows and sheep. If each field can have one sheep or one cow and never both, how many possible unique arrangements can you make such that, there are even number of sheep in the grid farm?