UMQL
      +---------
ZXVJU | YJRVJJRZ
       -ZXVJU
        =====
        XMPNRJ
       -XPLQPM
        ======
         XPWTZR
        -XHTHJQ
         ======
          XLPUZZ
         -XLXPYL
          ======
            HPWN

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium
missing: G