package main

import . "fmt"
import . "os"
import bf "bufio"
import "container/list"

func main() {
	rd := bf.NewReader(Stdin)
	var n int
	Fscan(rd,&n)
	nums := make([]*list.Element, n+1)
	ls := list.New()
	for i := 0; i < n; i++ {
		var p int
		Fscan(rd,&p)
		nums[p] = ls.PushBack(p)
	}
	ans := make([]any, 0, n)
	for i := 1; i <= n; i++ {
		e := nums[i]
		next := e.Next()
		if e == nil || next == nil {
			continue
		}
		ans = append(ans, e.Value, next.Value)
		ls.Remove(e)
		ls.Remove(next)
	}
	Println(ans...)
}