???????
      +--------
LFWNL | HHTXXQM
       -LFWNL
        =====
         FTNYQ
        -GHWXQ
         =====
         MPNJPM
        -UWHWPF
         ======
         ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: hard
missing: R