VLV
      +--------
UHGGT | WJNJRQM
       -YHMMP
        =====
        UTVLRQ
       -UJNZVP
        ======
          RZVQM
         -YHMMP
          =====
           ZZNM

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: challenging
missing: X