?????????
      +----------
YERXF | XXYFFLEMR
       -YERXF
        =====
         QXMFL
        -WTWQF
         =====
         HTRJLE
        -HFQMTF
         ======
          TFMYEM
         -HQFYNF
          ======
           JENMMR
          -JEFWRF
           ======
           ??????

base: 13
letters: EFHJLMNQRTWXY
difficulty: medium