/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */


public class Solution {
    /*
     * @param head: The first node of linked list.
     * @param n: An integer
     * @return: Nth to last node of a singly linked list.
     */
    public ListNode nthToLast(ListNode head, int n) {
        //set first node to position
        ListNode first = head;
        for (int i = 0; i<n;i++){
            first=first.next;
        }

        //increase first and second simultaneously until first comes to the end
        ListNode second = head;
        while(first!=null){
            first = first.next;
            second = second.next;
        }
        return second;
    }
}