23B
      +--------
C6BCC | A4A6635
       -C6BCC
        =====
        2278D3
       - 51455
        ======
         296DB5
        -2C01C4
         ======
          363EA

base: 15
letters: 0123456789ABCDE
difficulty: hard
hints: 3 << 4
missing: E