 start -> walk W 1
 walk -> start W 3
 start -> turn_right D 1
 turn_right -> start D 3
 turn_right -> turn_right_and_walk W 1
 turn_right_and_walk -> turn_right W 3
 turn_right_and_walk -> walk D 3
 start -> 1st_back R 1
 1st_back -> start 0 1
 
 