I spoke with a very nice lady at DR who answered this question for us:
DR stands for DONE RIGHT.
If you mean d*r = r*d (where * means multiply_ then it is the commutative property.
D in blackberry messenger means Delivered and R means Read!!
500 = D in Roman Numerals
Research & Development
It means 'define the relationship'
L,L,L,D,R,U,R,R,D,D,D,L,D,D,L,L,U,L,U,R,L,L,L,D,R,U,R,R,D,D,R,R,U,U,R,U,U,U, L,L,L,D,D,D,L,L,L,U,U,R,R,L,L,D,D,R,R,R,U,U,R,U,R,R,D,D,D,L,D,D,L,L,U,U,L,L,L, U,U,R,R,R,R,R,U,R,D,L,L,L,L,L,L,D,D,R,R,R,D,D,R,R,U,U,L,L,L,L,D,L,U,D,R,R.
U: Up D: Down L: Left R:Right The solution to the maze is: D-R-U-R-R-R-R-D-R D-L-D-L-L-L-L-D-L-D D-D-R-R-R-U-R-R-R-R U-L-U-R-R-R-D-D-D
In the answer, r is right l is left u is up d is down ------------- r u u r l u u u u u r u u d d r r r r d d r d l u r r d r r u r r d d d d d r r u u l d r d l u ------------- and your done
R,u,u,l,d,l,l,u,l,l,d,l,l,u,r,u,u,r,u,r,r,r,r,u,r,d,l,d,d,d,r,d,d,l,u,l,l,u,u,u,d,d,l,l,d,l,l, u,r,u,u,r,u,r,r,r,r,l,l,d,d,d,d,r,r,u,u,u,u,d,d,d,d,l,l,u,r,d,r,u,u,u,d,d,l,l,u,u,u,l,l,d,r, l,l,d,d,r,r,r,r,d,r,u,u,d,l,l,u,u,l,u,r.
U- Up D- down L- Left R- Right R,U,U,R,U,R,D,D,U,L,L,D,D,L,L,L,L,U,U,R,R,R,R,R,U,R,D,L,L,L,L,D,U,L,L,D,D,R,R,R,R,U,U,L,L,L, U,U,R,R,D,U,L,L,D,D,R,D,D,R,R,U,U,R,U,L,D,D,D,L,L,U,U,R,R,U,R,R,D,L,U,L,D,D,U,L,L,L,U,U,R,R, D,U,L,L,D,D,R,R,U,R,D.
l u u l u r r d l d d r u u l u u u l d d u u l l d d r l u r r u r d d d r d d l u u d d r r r u u l l d d r u r u l
This probably isn't the fastest solution to Soukoban level 51, but it works. L R R D L R R L L D L L R D L U R R R D L L R R R R L L U U R D L D R U R L L L U U L D R D L R R U U U L U R U L U R U L U L L R R D D D D D L R U L R U U L U L R R U L R D D D D L U U R U L D D D D R R R D D L D R L U U U U R L U R L U U R R L U R L D L L U R R L D D D R U L U R Hope I typed it right. Mieren Raje