UEUM
      +---------
GHGHJ | FHQQYNHH
       -GHGHJ
        =====
        GMLEFN
       -JYHYFN
        ======
          GYMMH
         -GHGHJ
          =====
           UQJNH

base: 12
letters: EFGHJLMNQUXY
difficulty: medium
missing: X