????????
      +---------
EQMQN | FJYMEJNE
       -XPEPJ
        =====
        RJMMUJ
       -RJPYPU
        ======
          NXRFN
         -EQMQN
          =====
          URNGPE
         -UJNFQF
          ======
          ??????

base: 13
letters: EFGHJMNPQRUXY
difficulty: intermediate
missing: H