If statement missing segment

Hi

I have data which looks like;

1	Case	w	x	y	z	aa
2	Case 1	Reason 1	Reason 2	Reason 3		0
3	Case 1	Reason 1	Reason 2	Reason 3	Reason 4	1
4	Case 2	Reason 1				0
5	Case 2	Reason 1	Reason 2			0

In AA is the following code.

=if(and(w2=w3,x2=x3,y2=y3,z2=z3),0,if(and(x2=x3,y2=y3,z2=z3),0,if(and(x2=x3,y2=0),0,if(and(y2=y3,z2=0),0,1))))

In AA5 I want to return 1 as the line relating to case 2 with the most information.

I know there is a section of code missing but I can't work out where.

Any help appreciated.