60th Belarusian Mathematical Olympiad problem

Problem

Exactly one integer number is written in each cell of an $8 \times 8$ square table. Per move it is allowed to choose any $n \times n$ square, $1 < n < 8$, and either to increase by 1 or to decrease by 1 all numbers in the cells of the chosen square. Is it possible to get the table with zeros in all its cells from the arbitrary initial table? (V. Kaskevich)