????????
      +---------
GUJQX | BQBHBGAU
       -BUAJA
        =====
         QGAGG
        -GUJQX
         =====
         JGGXAA
        -JGUXGX
         ======
           GUJBU
          -GUJQX
           =====
           ?????

base: 10
letters: ABFGHJKQUX
missing: F K
hints: H << F, F << K
difficulty: hard