????????
      +---------
JREEF | MQHEXNME
       -EHFFR
        =====
        PPNTPN
       - EHFFR
        ======
         XXLLQM
        -XUNXTT
         ======
          RHTHQE
         -RRXFLN
          ======
          ??????

base: 13
letters: EFHJLMNPQRTUX
difficulty: medium