1..12
ok 1 - (0, 0) => undef
ok 2 - (0, 1) => undef
ok 3 - (1, 0) => undef
ok 4 - (1, 1) => AB
ok 5 - (2, 1) => ABA
ok 6 - (3, 1) => ABAA
ok 7 - (4, 1) => ABAAA
ok 8 - (1, 2) => ABB
ok 9 - (2, 2) => ABBA
ok 10 - (7, 6) => ABABABABABABA
ok 11 - (3, 3) => ABBABA
ok 12 - (4, 14) => ABBBBBABBBBBABBBBA