????????
      +---------
RYPQP | UMGPJVNH
       -YXPGH
        =====
        XJNWYV
       -XNWMNV
        ======
         RVNJZN
        -RZMYWN
         ======
          RTWXZH
         -RVVYTG
          ======
          ??????

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