Question 100
The chessboard was split into domino tiles, meaning it was split into $1 \times 2$ and $2 \times 1$ rectangles. Each tile has a number written on it equal to the number of tiles that it has a common line segment with, without taking into account the tile itself. What is a least possible sum of all numbers that are written on the chessboard?
(Arsenii Nikolaiev)
(Arsenii Nikolaiev)