????????
      +---------
VXPWT | XJHGHPWY
       -YGJRL
        =====
        GQLVNP
       -GPZZHQ
        ======
         VUHYHW
        -GHQWMR
         ======
          VPLQQY
         -VLGLMJ
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard