?????????
      +----------
XHQNM | LLHXFYEXL
       -XHQNM
        =====
        UJJUXY
       -UMHHEJ
        ======
         WQNLXE
        -WXGHUG
         ======
           UEHFXL
          -UMHHEJ
           ======
           ??????

base: 14
letters: EFGHJLMNPQUWXY
hints: Y << H, L << P
missing: P
difficulty: challenging