????????
      +---------
UPYJN | HJRJJLJN
       -UPYJN
        =====
        QNQGGL
       -QWQLVQ
        ======
         WVXGQJ
        -QMZWJP
         ======
          QQJNHN
         -ZPWNUN
          ======
          ??????

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium
missing: T