load'strings' z=:3 :0 if.y=1 do.wd'XYZ'else.b=.<:g=.>.-:y wd@dtb"1(a{' X'),.(' Y'{~(g{.a),b#,:b{a=.(+.|.)f),.' Z'{~(|.f=.=i.y)+.#:>:2^y-1 end. ) z".1!:1[3