ドキドキ登山

#!/usr/bin/env ruby
#http://qiita.com/mtsmfm/items/6d9112fcc568908caaba
#http://mtsmfm.github.io/2016/06/04/doukaku-e04.html
#1630-1659

N=8

if __FILE__==$0
    while gets
        line=$_.chomp.split(':')
        a=line[0].reverse.chars.map{|e|[(e.to_i+N-1)%N,(e.to_i)%N]}
        idx1=line[1].ord-65
        (a.size-1).downto(0){|i|
            x=a[i].index(idx1)
            if x
                idx1=a[i][x^1]
                a[i][2]=true
            end
        }
        f=a.none?{|e|e[2]}
        puts N.times.select{|i|
            next false if f && i==idx1
            idx=i
            a.all?{|e|
                x=e.index(idx)
                !x || (!e[2] && idx=e[x^1])
            }
        }.map{|e|(e+65).chr}*''
        STDOUT.flush
    end
end