????????
      +---------
HJETR | TXNQRGRX
       -HJETR
        =====
        CEEHFG
       -CCXHTE
        ======
         XNTFJR
        -GQTRTC
         ======
          YTNRHX
         -YRXQRH
          ======
          ??????

base: 12
letters: CEFGHJNQRTXY
difficulty: medium