class ListNode:

def __init__(self, x):

self.val = x

self.next = None

class Solution:

def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:

# fast ,slow =head, head

# if n == 1 and not head.next:

# # print(n)

# return []

# while n:

# if fast is None:

# return None

# fast = fast.next

# n = n-1

# while fast.next:

# slow = slow.next

# fast = fast.next

# if not slow.next:

# return None

# slow.next = slow.next.next

# return head

if n == 1 and not head.next:

return None

fast, slow = head, head

while n and fast:

fast = fast.next

n -= 1

if not fast:

return head.next

while fast.next:

slow = slow.next

fast = fast.next

temp = slow.next.next

del slow.next

slow.next = temp

if __name__ == "__main__":

head = ListNode(1)

head.next=ListNode(2)

Solution().removeNthFromEnd(head, 1)

print(head.val)