????????
      +---------
FHGXF | JQWTWRFY
       -FHGXF
        =====
        MUFTTR
       -URTPXN
        ======
         FMGYUF
        -FPHRFN
         ======
          UHMRNY
         -URTPXN
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium
missing: L