12 2 1 1 2 3 1 ABC A B C ABC A B C ABC A B C 2 ABC A B C ABC A B C 3 ABC A B C 1 B C BC 2 B C BA BC A 3 A B A ABC A B C A B AB B C BC A C AC A B C ABC SSS ABC A B C ABC A B C SSS DBC BD DC ABD ACD ABD ACD SSS AB AC ADABCD ABD ACD 1 O OA OBC D AOB A O B AOB O D B C A 2 O A O OC O A C AOB A O B AOB O C A O D B C A 3 C CD 2D AOB A O B AOB O D C A O D B C A 4 D O B A O B AOB AOB A O B AOB O D B C A O D B C A 1 O OA OBC D 2 O A O OC O A C 3 C CD 2D 4 D O B A O B AOB AOB A O B AOB 1 2 3 SSS 12 21 9 ABC EFD AB EF AC ED B D C F 1 SSS ABC EFD 2 1 AB EF