[[[n,add2],[[v,a],[v,b]],":-",[[[n,=],[[v,a],[]]],[[n,=],[[v,b],[]]]]],[[n,add3],[[v,a],[v,b]],":-",[[[n,tail],[[v,a],[v,b]]]]],[[n,add0],[[v,a],[v,b]],":-",[[[n,1],[[v,a],[v,c]]],[[n,=],[[v,c],[v,b]]]]],[[n,1],[[v,a],[v,b]],":-",[[[n,add2],[[v,a],[v,c]]],[[n,=],[[v,c],[v,b]]]]],[[n,1],[[v,a],[v,b]],":-",[[[n,add3],[[v,a],[v,c]]],[[n,1],[[v,c],[v,d]]],[[n,=],[[v,d],[v,b]]]]]]