????????
      +---------
MHNHF | JMPRWWPJ
       -MHNHF
        =====
        QWHFTW
       -QWFWGU
        ======
          NTNNP
         -MHNHF
          =====
          UJGYFJ
         -ULPHQM
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
hints: F << L
missing: X