HGLN
      +---------
ZVYHU | PJYJGWLP
       -ZVYHU
        =====
        VTMTPW
       -VLTXGQ
        ======
         GTHJZL
        -GMWLUL
         ======
          XRRXMP
         -RYNUWY
          ======
           TYHUH

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium