????????
      +---------
WNUUU | RQXEEXXH
       -EQEEQ
        =====
         HQPJX
        -EQEEQ
         =====
         NHWGEX
        -NENXJT
         ======
          WJNTRH
         -NHTHHN
          ======
          ??????

base: 13
letters: EGHJMNPQRTUWX
difficulty: medium
hints: U << M
missing: M