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