ocaml, 126 bytes

Result

AC

Duration

979ms

Code [DL]

let(b,a)=(read_int()-2,read_int())let _=for i=1 to a do
print_endline("*"^String.make b(if i=1||i=a then '*'else ' ')^"*")done

stdin

15
19

stdout

*******************
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*                 *
*******************

stderr