The numbers 1 through 16 can be written into a four-by-four grid so that each number is vertically, horizontally, or diagonally adjacent to the number before it. The numbers in the shaded squares are given. 1 16 3 9 15 5 11 Eva starts to fill in the puzzle, but she makes a mistake and cannot decide how to continue. 2 1 16 3 9 4 15 6 5 11