# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def mergeKLists(self, lists):
        """
        :type lists: List[ListNode]
        :rtype: ListNode
        """
        if not lists:
            return None
        res=[]
        for a in lists:
            while a:
                res.append(a.val)
                a=a.next
        res.sort()
        p=ListNode(0)
        q=p
        for i in range(0,len(res)):
            q.next=ListNode(res[i])
            q=q.next
        return p.next