MQLU
      +---------
WHMTN | YRJZMRLH
       -WHMTN
        =====
        NVGGPR
       -NLVGJX
        ======
         GVXYRL
        -GJNVMT
         ======
          WQMWHH
         -WTJLZQ
          ======
           JPUJG

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