a-a a-b a-c aaa aab aac aad aar ab- aba abb abc abd abr ac- aca acb acc acd acr ad- ada adb adc add adr ar- ara arb arc ard arr baa bab bac bad bar bba bbb bbc bbd bbr bca bcb bcc bcd bcr bda bdb bdc bdd bdr bra brb brd brr c-- caa cab cac cad car cba cbb cbc cbd cbr cca ccb ccc ccd ccr cda cdb cdc cdd cdr cra crb crc crd crr daa dab dac dad dar dba dbb dbc dbd dbr dca dcb dcc dcd dcr dda ddb ddc ddd ddr dra drb drc drd drr ra- raa rab rac rad rar rba rbb rbc rbd rbr rca rcb rcc rcd rcr rda rdb rdc rdd rdr rra rrb rrc rrd rrr