Get Nth element from the end in a linked list

GetNode.cpp

/*
  Get Nth element from the end in a linked list of integers
  Number of elements in the list will always be greater than N.
  Node is defined as 
  struct Node
  {
     int data;
     struct Node *next;
  }
*/
int GetNode(Node *head,int k)
{
    if(head == NULL) return -1;
 	Node *p1 = head;
	Node *p2 = head;
		
    for (int i = 0 ; i < k ; i++) {
		if(p2 == NULL) return -1;
		p2 = p2->next;
	}
	
	if( p2 == NULL) return -1;
	
	while(p2->next != NULL) {
		p1 = p1->next;
		p2 = p2->next;
	}
	return p1->data;
}