????????
      +---------
MTFNR | LWFHNTWR
       -MTFNR
        =====
        TLGQMT
       -TJLFNP
        ======
         QTNXPW
        -QQHNRT
         ======
          PHUULR
         -PLQHUG
          ======
          ??????

base: 14
letters: FGHJLMNPQRTUWX
difficulty: challenging