UFWN
      ----------
 NWNN ) UFXECQFC
       -QNHNF
        =====
         FWEUQ
        -HNQNU
         =====
          WWUNF
         -FNENQ
          =====
           NQCXC
          -WNCNE
           =====
            QNXN

base: 10
symbols: ACEFHNQUWX
difficulty: intermediate
missing: A