Find the number of nodes at level of x and above

I want to find number the of nodes that are in the same level as the node with @title="d" or are in the higher level

XML:

<item title="a">
       <item title="b">               
           <item title="c"></item>
           <item title="d">  
               <item title="e"></item>  
               <item title="f"></item>
           </item>                 
       </item> 
       <item title="x">             
           <item title="y"></item> 
           <item title="z"></item>  
       </item>            
</item> 

L0 . . . . . .  a . . . .
              /   \
L1 . . . . . b . . x .  .
           /  \   / \
L2 . . . .c . d .y . z  .
             / \
L3 . . . . .e . f . . . .

Some examples:

System.out.println(leftDomainSize("d")); // 7
System.out.println(leftDomainSize("x")); // 3
System.out.println(leftDomainSize("e")); // 9

Code:

public int leftDomainSize(String s){
        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
        Document document = documentBuilder.parse(path);
        //????
}