????????
      +---------
RQPUP | NYWTZWMR
       -NNNYN
        =====
         LNGHW
        -PRYRQ
         =====
         RJNPZM
        -RRQLQM
         ======
          RLTGVR
         -RLZNZG
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
hints: W << Z, N << H
missing: X