????????
      +---------
RUXHQ | XTHWNTPL
       -UUHGL
        =====
         QMQPT
        -UUHGL
         =====
         TUPXGP
        -TUXFWJ
         ======
           YGYUL
          -YMRXF
           =====
           ?????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium