WXQH
      +---------
TRRRN | PXWGXWNU
       -JYYZH
        =====
        RLZPHW
       -LULLYR
        ======
         RHJQPN
        -RRGGXU
         ======
          WLHVXU
         -VUZZXW
          ======
           LXYMQ

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