PYUH
      +---------
JMGLP | UUQGXMPH
       -JMGLP
        =====
        WYHXNM
       -WQJWWY
        ======
         PQJPHP
        -PUHTGU
         ======
          JNWFQH
         -JWLGPH
          ======
           PMJMF

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