Problem A magic square is a square array of natural numbers whose rows, columns, and diagonals all sum to the same number. For example, the following is a 3 by 3 magic square where the sums of the numbers in a row, a column, or a diagonal are all equal to 15. Prove that it is impossible to construct a 3 by 3 magic square of the form where every digit from 1 to 9 appears in this square one and only one time.