?????????
      +----------
TGLJZ | MMYTGWYLV
       -ZUMLG
        =====
         UNQNW
        -PRUZW
         =====
          VJYNY
         -TGLJZ
          =====
          JLLGJL
         -JTNWWQ
          ======
           XLMUWV
          -XTZLUT
           ======
           ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: intermediate
missing: H