????????
      +---------
QYYEY | MQWJEFMJ
       -QYYEY
        =====
        QUEFXF
       -QPELNG
        ======
         QLQGPM
        - NYUUE
         ======
          QUMNWJ
         -QPELNG
          ======
          ??????

base: 13
letters: EFGJLMNPQUWXY
difficulty: medium