public class ListNode {

    int val;

    ListNode next = null;

    ListNode(int val) {

        this.val = val;

    }

public class Solution {

    public ListNode FindKthToTail(ListNode head,int k) {

        ListNode p = head;

        ListNode pre = head;

        int a =k;

        int count = 0;

        while(p != null){

            p = p.next;

            count ++;

            if(k <1){

                pre = pre.next;

            }

            k--;

        }

        if(count < a){

            return null;

        }

        return pre;

    }

}