eval"R,B=%d,%d
D={}
f=->s{n=s.size
D[s]||=$.<n&&(0...n).any?{|i|[[?R,i-R],[?B,i-B]].any?{|c,j|s[i]==c&&j>=0&&s[j]==c}}?n.times{|i|s[i]>?R||f[s[0,i]+s[i+1,n]]}:n>$.&&$.=n}
f['%s']
p$."%`dd`.split