This question is just a puzzle, so clearly off-topic here, but still it's funny to find answer :-)
For this specific maze there exists sequence of moves that we end up in S.
! a) 12*D - and we can end up on top of any +:
+ + + + + + + + + + + + + + + + + + + + + + + + +
+ _ @ @ _ @ @ _ + _ @ @ _ @ @ _ + _ @ @ _ @ @ _ +
+ _ + + _ + + _ + _ + + _ + + _ + _ + + _ + + _ +
+ _ + _ _ _ + _ + _ + _ _ _ + _ + _ + _ _ _ + _ +
+ _ + @ @ @ + _ + _ + @ @ @ + _ + _ + @ @ @ + _ +
+ _ + + + + + _ + _ + + + + + _ + _ + + + + + _ +
+ @ @ @ @ @ @ _ @ @ @ @ @ @ @ @ @ _ @ @ @ @ @ @ +
+ + + + + + + _ + + + + + + + + + _ + + + + + + +
+ _ @ @ _ @ @ _ @ _ @ @ _ @ @ _ @ _ @ @ _ @ @ _ +
+ _ + + _ + + _ + _ + + _ + + _ + _ + + _ + + _ +
+ _ + _ _ _ + _ + _ + _ _ _ + _ + _ + _ S _ + _ +
+ _ + @ @ @ + _ + _ + @ @ @ + _ + _ + @ @ @ + _ +
+ _ + + + + + _ + _ + + + + + _ + _ + + + + + _ +
+ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ +
+ + + + + + + + + + + + + + + + + + + + + + + + +
! b) 22*L
+ + + + + + + + + + + + + + + + + + + + + + + + +
+ @ _ _ _ _ _ _ + @ _ _ _ _ _ _ + @ _ _ _ _ _ _ +
+ _ + + _ + + _ + _ + + _ + + _ + _ + + _ + + _ +
+ _ + _ _ _ + _ + _ + _ _ _ + _ + _ + _ _ _ + _ +
+ _ + @ _ _ + _ + _ + @ _ _ + _ + _ + @ _ _ + _ +
+ _ + + + + + _ + _ + + + + + _ + _ + + + + + _ +
+ @ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ +
+ + + + + + + _ + + + + + + + + + _ + + + + + + +
+ @ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ +
+ _ + + _ + + _ + _ + + _ + + _ + _ + + _ + + _ +
+ _ + _ _ _ + _ + _ + _ _ _ + _ + _ + _ S _ + _ +
+ _ + @ _ _ + _ + _ + @ _ _ + _ + _ +@_ _ _ + _ +
+ _ + + + + + _ + _ + + + + + _ + _ + + + + + _ +
+ @ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ +
+ + + + + + + + + + + + + + + + + + + + + + + + +
! 1020