function preOrder(root) {
    if (root !== null) {
        process.stdout.write(root.data + " ");
        preOrder(root.left);
        preOrder(root.right);
    }
}

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
)

type Node struct {
	Value int
	Left  *Node
	Right *Node
}

func printTree(node *Node) {

	fmt.Printf("%d ", node.Value)

	if node.Left != nil {
		printTree(node.Left)
	}

	if node.Right != nil {
		printTree(node.Right)
	}	
}

func insertNode(node *Node, value int) {
	if node.Value > value {
		if node.Left == nil {
			node.Left = &Node{
				Value: value,
			}
			return
		}

		insertNode(node.Left, value)
	} else {
		if node.Right == nil {
			node.Right = &Node{
				Value: value,
			}
			return
		}

		insertNode(node.Right, value)
	}
}

func contructTree(nodes []int) *Node {

	// 1 <=  nodes in the tree 
	root := &Node{
		Value: nodes[0],
	}

	for i := 1; i < len(nodes); i++ {
		insertNode(root, nodes[i])
	}

	return root
}

func main() {
	reader := bufio.NewReaderSize(os.Stdin, 16*1024*1024)

	readLine(reader)
	input := strings.TrimSpace(readLine(reader))
	stringNodes := strings.Split(input, " ")

	nodes := make([]int, len(stringNodes))
	for i, node := range stringNodes {
		nodes[i], _ = strconv.Atoi(node)
	}

	root := contructTree(nodes)
	printTree(root)
}

func readLine(reader *bufio.Reader) string {
	str, _, err := reader.ReadLine()
	if err == io.EOF {
		return ""
	}

	return strings.TrimRight(string(str), "\r\n")
}

func checkError(err error) {
	if err != nil {
		panic(err)
	}
}

def preOrder(root):
    if root:
        print(root, end=' ')
        preOrder(root.left)
        preOrder(root.right)