VZH
      +--------
GXVWP | PUUHQTH
       -XNGGL
        =====
        QMHVNT
       -QQNRYQ
        ======
         YVVVUH
        -VUJGMH
         ======
          QHUNR

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