WHQU
      ----------
 UQUU ) WHYNFXHF
       -XUEUH
        =====
         HQNWX
        -EUXUW
         =====
          QQWUH
         -HUNUX
          =====
           UXFYF
          -QUFUN
           =====
            XUYU

base: 10
symbols: CEFHNQUWXY
difficulty: intermediate
missing: C