There are k slots numbered 1 through k, and you must assign a distinct integer between 1 and n, inclusive, to each slot. The resulting configuration is called an arrangement of k from n. An example of an arrangement of 3 from 5 is (2, 4, 3).
An arrangement is called unfixed if no integer is equal to the number of its slot. For example, the arrangement (2, 4, 3) is not unfixed because the integer 3 is in slot number 3. The arrangement (2, 4, 5), on the other hand, is unfixed.
Given ints n and k, return the number of unfixed arrangements of k from n.