????????
      +---------
LTTYY | GYNHWZLR
       -GNPHX
        =====
         MWJPZ
        -LTTYY
         =====
         TGYMUL
        -TXWNJH
         ======
          UZNJHR
         -UMMHQN
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: challenging
hints: L << R
missing: V