class TreeNode:
def __init__(self, value):
self.value = value
self.left = None
self.right = None
def build_tree(numbers):
root = TreeNode(numbers[0])
for num in numbers[1:]:
current = root
while True:
if num < current.value:
if current.left:
current = current.left
else:
current.left = TreeNode(num)
break
else:
if current.right:
current = current.right
else:
current.right = TreeNode(num)
break
return root
def preorder_traversal(node):
if not node:
return
print(node.value, end=' ')
preorder_traversal(node.left)
preorder_traversal(node.right)
try:
while True:
N = int(input())
numbers = list(map(int, input().split()))
tree_root = build_tree(numbers)
preorder_traversal(tree_root)
print()
except EOFError:
pass