Choose elements from array randomly in matlab and store the remain element

I have array contain 1 column with 225 rows and I want to select 170 elements from these elements randomly and store it in another array also store the remain elements at another array, I used this code to choose randomly elements but I don't know how I can store the remain elements (55) at another array !

Code : my original array A

msize = numel(A);
firstpart = A(randperm(msize, 170))

secondpart = !!!!! ( remain elements ) % This is my question