from X cons X from s X head cons X XS X 2nd cons X XS head XS take 0 XS nil take s N cons X XS cons X take N XS sel 0 cons X XS X sel s N cons X XS sel N XS 2.2 take s N cons X XS take N XS 2nd cons X XS head XS sel s N cons X XS sel N XS from X from s X true from X from s X true Failed! NaTT certifiable-1.6