As long as you have complied with the F-1 visa conditions, your exempt status terminates on 12/31/2018 -- five calendar years , including the year of admission. Thus for 2018, you still file a 1040-NR. from 2019 Jan 1st , you start counting days present ( because your exempt status is no longer valid).
Also there is no form 1040-A for 2018 onwards --- it is only 1040 and schedules 1 through 7 to cater for the different requirements for the filers.
Hope this helps