M knows about adding small numbers on his fingers. I tried to connect that with the numbers laid out in a sequence on the table, so he could see that +1 means 1 to the right, and -1 means 1 to the left. This will take more work, but it was a good introduction. R liked it too.
Yemina, yemina, smola smol
Lemata, lemata, lemala, lemala
(Right, Left, Front, Back, Down, Up, in our Sukkah!)
And here are M and R drawing in the Sukkah: