????????
      +---------
MNMNN | UNHLGPUR
       -MNMNN
        =====
        LJURQP
       - QTQQT
        ======
         LGGXUU
        -LYGYFR
         ======
          MJHWXR
         -MJLJMT
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium
hints: F << N