Let $x$ and $y$ be odd positive integers. A table $x$ x $y$ is given in which the squares with coordinates $(2,1)$, $(x - 2, y)$, and $(x, y)$ are cut. The remaining part of the table is covered in dominoes and squares 2 x 2. Prove that the dominoes in a valid covering of the table are at least $\frac{3}{2}(x+y)-6$