zeros cons 0 n__zeros and tt X activate X length nil 0 length cons N L s length activate L take 0 IL nil take s M cons N IL cons N n__take M activate IL zeros n__zeros take X1 X2 n__take X1 X2 activate n__zeros zeros activate n__take X1 X2 take X1 X2 activate X X 2.2 take s M cons N IL activate IL length cons N L activate L length cons N L length activate L activate n__zeros zeros and tt X activate X activate n__take X1 X2 take X1 X2 true and tt X activate X false length cons N L length activate L true Failed! NaTT certifiable-1.6