????????
      +---------
UQNGG | WHLMXXJU
       -VRGGL
        =====
        UPQTJX
       - JLRRW
        ======
         URMLHJ
        -UWZNGU
         ======
          ULHYQU
         -UXUZGM
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard