GMQH
      +---------
XRVTW | RVZRYTQW
       -XRVTW
        =====
        GQZZVT
       -GXZJQH
        ======
         YVLRJQ
        -YZNLGQ
         ======
          MXPLUW
         -MGWZTM
          ======
           MRGXV

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard