????????
      +---------
LTLPJ | UJQTJQLP
       -UZULX
        =====
         JLNVQ
        -XZXUR
         =====
         VHWPXL
        -VVPHVY
         ======
           GURTP
          -QTQGG
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
hints: Q << R
missing: M