????????
      +---------
JWHRU | PPUUTPJP
       -JWHRU
        =====
        XPNJPP
       -XYTYNJ
        ======
          FHFJJ
         -UWLMW
          =====
          JTQLRP
         -JNHUXM
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
missing: G