????????
      +---------
MMULJ | MYVWQPRT
       -MMULJ
        =====
         JUHMP
        -JYLZG
         =====
          JHJPR
         -HQHZN
          =====
           PMGZT
          -ZJLVG
           =====
           ?????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium
hints: R << T
missing: X