import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
public class New {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int len=sc.nextInt();
        List<Integer> arr=new ArrayList<>(len);
        List<Integer> result=new ArrayList<>(len);
        for(int i=0;i<len;i++){
            arr.add(sc.nextInt());
        }
        while(!arr.isEmpty()){
            Value min=findMin(arr);
            result.add(min.a);
            result.add(min.b);
            arr.remove(min.offset);
            arr.remove(min.offset);
        }
        StringBuilder builder=new StringBuilder(result.size()*4);
        for(Integer c:result){
            builder.append(c).append(" ");
        }
        System.out.println(builder.toString().replaceFirst(" $",""));
    }
    private static Value findMin(List<Integer> arr){
        Integer minA=Integer.MAX_VALUE;
        Integer minB=Integer.MAX_VALUE;

        int offset=-1;

        Integer prev=arr.getFirst();
        for(int i=1,size=arr.size();i<size;i++){
            if(minA<prev){
                prev=arr.get(i);
                continue;
            }
            if(minA.equals(prev) &&minB<=arr.get(i)){
                prev=arr.get(i);
                continue;
            }
            minA=prev;
            minB=arr.get(i);
            prev=minB;
            offset=i-1;
        }
        return new Value(minA,minB,offset);
    }
    private record Value(Integer a, Integer b, int offset){}
}