????????
      +---------
XPFXP | RGFJHFPP
       -QEQTF
        =====
         FYPLF
        -FGGLQ
         =====
          XFNYP
         -XPFXP
          =====
           JXENP
          -RQTRX
           =====
           ?????

base: 13
letters: EFGHJLNPQRTXY
difficulty: medium