QMQ
      +--------
TRMWG | NLJVTGL
       -TRMWG
        =====
        QYZRHG
       -QYPJXH
        ======
          TZNJL
         -TRMWG
          =====
           XRQG

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: challenging
hints: P << Q, T << G
missing: U