????????
      +---------
LJHXN | CPKTLLBB
       -KPLLK
        =====
        BXJXJL
       -BXBPTP
        ======
          THBPB
         -LJHXN
          =====
           CKJLB
          -KPLLK
           =====
           ?????

base: 10
letters: BCHJKLNPTX
difficulty: hard