merge nil nil X X merge nil cons Y U V merge U nil cons Y V merge cons W P X1 Y1 merge X1 P cons W Y1 map G1 nil nil map H1 cons W1 P1 cons H1 W1 map H1 P1 X list Y nat U list V list W nat P list X1 list Y1 list G1 nat nat H1 nat nat W1 nat P1 list cons nat list list map nat nat list list merge list list list list nil list FULL benchmarks/mine/merge.aidts