a-a a-b a-c aaa aab aac aad aae aaf aak ab- aba abb abc abd abe abf abk ac- aca acb acc acd ace acf ack ad- ada adb adc add ade adf adk aea aeb aec aed aee aef aek af- afa afb afc afd afe aff afk aka akb akc akd ake akk baa bab bac bad bae baf bak bba bbb bbc bbd bbe bbf bbk bca bcb bcc bcd bce bcf bck bda bdb bdc bdd bde bdf bdk be- bea beb bec bed bee bef bek bfa bfb bfc bfd bfe bff bka bkb bkc bke bkf bkk c-- caa cab cac cad cae caf cak cba cbb cbc cbd cbe cbf cbk cca ccb ccc ccd cce ccf cck cda cdb cdc cdd cde cdf cdk ce- cea ceb cec ced cee cef cek cfa cfb cfc cfd cfe cff cfk cka ckb ckc ckd daa dab dac dad dae daf dak dba dbb dbc dbd dbe dbf dbk dca dcb dcc dcd dce dcf dck dda ddb ddc ddd dde ddf ddk de- dea deb dec ded dee def dek dfa dfb dfc dfd dfe dff dfk dka dkb dkc dke dkk eaa eab eac ead eae eaf eak eba ebb ebc ebd ebe ebf ebk ec- eca ecb ecc ecd ece ecf eck ed- eda edb edc edd ede edf edk eea eeb eec eed eee eef eek ef- efa efb efc efd efe eff eka ekb ekc ekd eke ekf faa fab fac fad fae faf fak fba fbb fbc fbd fbe fbf fbk fca fcb fcc fcd fce fcf fck fda fdb fdc fdd fde fdf fdk fea feb fec fed fee fef fek ffa ffc ffd ffe fff ffk fka fkb fkc fkf fkk ka- kaa kab kac kad kae kaf kak kba kbb kbc kbd kbe kbf kbk kca kcb kcc kcd kce kck kda kdb kdc kde kdf kdk ke- kea keb kec ked kee kef kek kfa kfc kfd kff kkb kkc kke kkk