movement rule: right-else-straight-else-left-else-stop
               =======================================

this robot follows the wall, so every cycle needs its own wall

permutation      no indoor walls           indoor walls allowed
-----------      ---------------           --------------------
                    _ _
(1)              1_|   |                   same
                 |_ _ _|

                 1_ _2
(12)             |_ _|                     same

                    _ _ _
(1)(2)            _|  _  |                  _ _ _
                 |  _|_| |_                |  _  |_
              2> | |_|_   _|            2> | |_   _|
                 |_  |_| | 1               |_ _ _| 1
                   |_ _ _|

                   1_
(123)            2_| |_3                   same
                 |_ _ _|

                    _ _ _
                  _|  _  |_3                _ _ _ _3
                 |  _|_|  _|               |  _   _|
(1)(23)          | |_|_  |_  <1            | |_  |_  <1
                 |_  |_|  _|               |_ _ _ _|
                   |_ _ _| 2                       2

                   _ _ _ _ _
(1)(2)(3)        _|  _   _  |_              _ _ _ _ _ _1
                |  _|_| |_|_  |            |  _   _   _|
            2> _| |_|_   _|_| | <3      3> |  _| |_  |   <2
              |_ _  |_| |_|  _|            |_ _ _ _ _|
              1   |_ _ _ _ _|

                    _4
(1234)           1_| |_                    same
                 |_   _|
                   |_| 3
                   2

                    _ _ _ _4
(1)(234)          _|  _   _|                _ _ _ _4
                 |  _|_| |_3               |  _   _|
                 | |_|_   _| <<1        1> |  _|  _| 3
                 |_  |_| |_2               |_ _ _ _|
                   |_ _ _ _|                       2

                  _ _ _ _ _ _1
                 |  _   _   _|              _ _ _ _ _1
(12)(34)      4> | |_|_|_| |_              |  _ _   _|
              3> |  _|_|  _ _|          4> |  _|_  |_  <3
                 | |_|  _|   2             |_ _ _ _ _|
                 |_ _ _|                             2

                     _ _ _ _ _
(1)(2)(34)      4_ _|  _   _  |_            _ _ _ _ _ _3
                |_   _|_| |_|_  |          |  _   _   _|
              1> _| |_|_   _|_| | <2    1> |  _| |_  |_  <2
                |_ _  |_| |_|  _|          |_ _ _ _ _ _|
                3   |_ _ _ _ _|                        4

                     _ _ _ _ _ _ _ _
(1)(2)(3)(4)       _|  _   _     _  |_      _ _ _ _ _ _ _ _1
                  |  _|_| |_|_  |_|_  |    |  _       _   _|
              2> _| |_|_   _|_|  _|_| |    |  _| |_| |_  |
                |_ _  |_| |_|   |_|  _|    |_ _ _ _ _ _ _|
                1   |_ _ _ _ _ _ _ _|         ^   ^   ^
                       ^   ^     ^            2   3   4
                       2   3     4

(12345)            _5  _4                    5_ _4
                1_| |_| |                   _| | |
                |_   _  |                  |_    |
                  |_| |_|                  1 |_|_|
                  2   3                      2   3

                     _ _ _ _4
(1)(2345)          _|  _   _|              5_ _ _ _ _4
                5_|  _|_| |_3              |_   _   _|
                |_  |_|_   _| <<1        1>  |  _|  _| 3
                  |_  |_| |_2                |_ _ _ _|
                    |_ _ _ _|                        2

                    _6  _5                   6_ _5
(123456)         1_| |_| |_                 _| | |_
                 |_   _   _|               |_     _|
                   |_| |_| 4               1 |_|_| 4
                   2   3                     2   3