a-a a-b a-c aaa aab aac aad aak aan ab- aba abb abc abd abk abn ac- aca acb acc acd ack acn ad- ada adb adc add adk adn aka akb akc akd akk akn an- ana anb anc and ank ann baa bab bac bad bak ban bba bbb bbc bbd bbk bbn bca bcb bcc bcd bck bcn bda bdb bdc bdd bdk bka bkb bkc bkk bkn bna bnb bnc bnd bnk bnn c-- caa cab cac cad cak can cba cbb cbc cbd cbk cbn cca ccb ccc ccd cck ccn cda cdb cdc cdd cdk cdn cka ckb ckc ckd cn- cna cnb cnc cnd cnn daa dab dac dad dak dan dba dbb dbc dbd dbk dbn dca dcb dcc dcd dck dcn dda ddb ddc ddd ddk ddn dka dkb dkc dkk dna dnb dnc dnd dnk dnn ka- kaa kab kac kad kak kan kba kbb kbc kbd kbk kbn kca kcb kcc kcd kck kcn kda kdb kdc kdk kkb kkc kkk kkn kn- kna knc knd knk knn naa nab nac nad nak nan nba nbb nbc nbd nbk nbn nca ncb ncc ncd nck ncn nda ndb ndc ndd ndk ndn nka nkc nkk nkn nna nnb nnc nnk nnn