YXN
      +--------
MRRGN | QQMNQTF
       -MRRGN
        =====
        XHUXTT
       -YPLLHJ
        ======
         GJGTYF
        -GYLGPW
         ======
          YMMGU

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium