The numbers 1 to 64 are written in order on the chessboard above. What is the sum of the numbers in the yellow squares minus the sum of the numbers in the white squares?
0 is the answer,
64 numbers (not necessarily distinct) are placed on the squares of a chessboard such that the sum of the numbers in every 2x2 square is 7.
What is the sum of the four numbers in the corners of the board?
