GZY
      +--------
VLNMG | HRVUUPW
       -VLNMG
        =====
        QQXPVP
       -JNWTPZ
        ======
         NVZYRW
        -NXYUJY
         ======
          NWQLR

base: 16
letters: GHJLMNPQRTUVWXYZ
difficulty: medium