????????
      +---------
PHWRU | RNJYHWYY
       -NGXWX
        =====
        VPVZVW
       - QJJNX
        ======
         PYLWUY
        -PUXTYX
         ======
          PYMWQY
         -PYPHTW
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
hints: T << M