/**

 * Definition for singly-linked list.

 * public class ListNode {

 *     int val;

 *     ListNode next;

 *     ListNode(int x) { val = x; }

 * }

 */

public class Solution {

    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {

        ListNode p1 = l1;

        ListNode p2 = l2;

        ListNode fakeHead = new ListNode(0);

        ListNode p = fakeHead;

        while (p1 != null && p2 != null) {

            if (p1.val <= p2.val) {

                p.next = p1;

                p1 = p1.next;

            } else {

                p.next = p2;

                p2 = p2.next;

            }

            p = p.next;

        }

        if (p1 != null) {

            p.next = p1;

        }

        if (p2 != null) {

            p.next = p2;

        }

        return fakeHead.next;

    }

}