??????
     +-------
REQM | UXGGQH
      -FWHF
       ====
       JWQJQ
      -JHQLE
       =====
        RLLMH
       -JUJGX
        =====
        ????X

base: 13
letters: EFGHJLMNQRUWX
difficulty: medium
hints: F << M
missing: N