YUVY
      +---------
QQPMP | QGLTWXHJ
       -QQPMP
        =====
         NWYYX
        -MMJQX
         =====
         YVUHZH
        -YJHJTN
         ======
           PYLTJ
          -QQPMP
           =====
           YHWYL

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: hard
missing: R