NTJ
      +--------
NZJYL | VVXNXQW
       -NZJYL
        =====
        NRJMWQ
       -NVRVUH
        ======
         NQXJJW
        -NQGTZZ
         ======
           XYZU

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