?????????
      +----------
JHTLJ | PQVQVJMLP
       -JHTLJ
        =====
         ZXXMJ
        -WQNHG
         =====
         TWYMVM
        -TMMMJZ
         ======
          JVRNGL
         -JMPRXV
          ======
           TUNRWP
          -TWNGGY
           ======
           ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium