30 50
ADC ADD BAA BAB BAC BAD BBA BBB BBC BBD BCA BCB BCC BCD BDA BDB BDC BDD CAA CAB CAC CAD CBA CBB CBC CBD CCA CCB CCC CCD CDA CDB CDC CDD DAA AB AC AD BA BB BC BD CA CB CC CD DA B C D 
ADB ADC ADD BAA BAB BAC BAD BBA BBB BBC BBD BCA BCB BCC BCD BDA BDB BDC BDD CAA CAB CAC CAD CBA CBB CBC CBD CCA CCB CCC CCD CDA CDB CDC CDD AA AB AC AD BA BB BC BD CA CB CC CD A B C