sqlite3, 195 bytes

Result

AC

Duration

1037ms

Code [DL]

with x(i,j,k)as(select v+0 i,substr(v,instr(v,'
')+1)j,1 k from i union select i,j,k+1 from x)select printf('*%.'||(j-2)||'c*',case when(k=1 or k=i)then'*'else' 'end)from x limit(select i from x)

stdin

31
31

stdout

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

stderr