Permution & C

Question

There are four persons wearing different colour shirts and four gift packs of colours, same as
those of the shirts. The number of ways in which the gifts, one each to a person, could be
given such that a gift does not go to a person of his shirt colour is

Answer 1

It is a derangement problem

Formula here used is 4!(1 - 1/1! +1/2! -1/3! +1/4!) =9

Answer is 9