Return an array that contains exactly the same numbers as the given array, but rearranged so that every 4 is immediately followed by a 5. Do not move the 4s, but every other number may move. The array will contain the same number of 4s and 5s, and every 4 will have a number after it that is not another 4. For example, if the input is {5, 4, 9, 4, 9, 5}, the output should be {9, 4, 5, 4, 5, 9}. The 4s stay in place, and the 5s are placed immediately after each 4. The rest of the numbers may move around.