A rectangle 3×5 is divided into 15 1×1 cells. The middle 3 cells that have no common points with the border of the rectangle are deleted. Is it possible to put in the remaining 12 cells numbers 1,2,…,12 in some order, so that the sums of the numbers in the cells along each of the four sides of the rectangle are equal?Proposed by Mariia Rozhkova permutationsrectangleMagic squares