# Definition for singly-linked list.

 # class ListNode(object):

 #     def __init__(self, x):

 #         self.val = x

 #         self.next = None

 class Solution(object):

     def removeNthFromEnd(self, head, n):

         """

         :type head: ListNode

         :type n: int

         :rtype: ListNode

         """

         dummy = ListNode(-1)

         dummy.next = head

         cur, slow = dummy, dummy

         while n > 0:

             cur = cur.next

             n -= 1

         while cur.next is not None:

             slow = slow.next

             cur = cur.next

         slow.next = slow.next.next

         return dummy.next