MJTG
      +---------
ZTNJY | XTWNVGTP
       -NQXRT
        =====
        ZLRWMG
       -ZYMZTY
        ======
         ZMGRXT
        -ZWLPVH
         ======
          ZRJUTP
         -ZLVUPN
          ======
            GHMW

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: challenging