????????
      +---------
JTPYG | UZQYVRLJ
       -JTPYG
        =====
        HHPUZR
       -HXTGZM
        ======
         NRRMRL
        -YUVRVG
         ======
          GNWXTJ
         -RPYPNM
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium