Both are accepted now. June 2018. On the right and to the right are both correct.
I wrote " la tercera puerta a a la derecha" - I put an extra "a" by accident, but the solution I think is correct, and it was not accepted. In other cases typos are accepted.
It's amazing how literal this is to what we say in English, now I'm starting to see why they say Spanish is one of the easiest languages for English speaker