sqlite3, 190 bytes

Result

AC

Duration

1048ms

Code [DL]

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

stdin

60
26

stdout

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

stderr