????????
      +---------
YXXXG | UXZMTNXY
       -YXXXG
        =====
         JRURN
        -YXXXG
         =====
         NNZZJX
        -NMUUUQ
         ======
          WHPZXY
         -WZLLLR
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
missing: V