Given the IntNode class, define the IndexOf$()$ function to return the index of parameter target or $-1$ if not found.

Note: The first index after the head node is $0.$

Ex: If the list contains:

head $->14->191->22->99$

IndexOf$($headNode$,22)$ returns $2.$

Ex: If the list contains:

head $->$

IndexOf$($headNode$,22)$ returns $-1.$