#include<iostream>
#include<algorithm>
using namespace std;
int a[21];
int main(){
	for(int i=0;i<20;i++)cin>>a[i];
	sort(a,a+20);
	for(int i=0;i<20;i+=2)cout<<a[i]<<" ";
	return 0;
}

#include<bits/stdc++.h>

using namespace std;

int A[118];

int main(){

int n;

for(int i = 1;i<=20;i++){

cin>>A[i]; }

sort(A + 1,A + 1 + 20);

for(int i = 1;i<=19;i+=2){

cout << A[i]<<" "; }

}

#include<iostream>

#include<bits/stdc++.h>

using namespace std;

int a[114];

int main(){

for(int i=1;i<=20;i++){

cin>>a[i];

} sort(a+1,a+20+1);

for(int i=1;i<=20;i+=2){

cout<<a[i]<<" ";

}

return 0;

}

#include <bits/stdc++.h>
using namespace std;
const int N=1e5+10;
const int INF=0x3f3f3f3f;
int a[N],s[N],ans;
bool f;
int main()
{
	for(int i=1;i<=20;i++)
	{
		cin>>a[i];
	}
	sort(a+1,a+21);
	for(int i=1;i<=20;i+=2)
	{
		cout<<a[i]<<" ";
	}
	return 0;
}

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int a[N];
int main()
{
	int	n = 20;
	for(int i = 0;i < 20;i++)
		cin >> a[i];
	for(int i = 0;i < n-1;i++)
	{
		for(int j = 0;j < n-i-1;j++)
		{
			if(a[j] > a[j+1])
			{
				int t = a[j];
				a[j] = a[j + 1];
				a[j+1] = t;
			}
		}
	}
	for(int i = 0 ; i < n ; i+=2)
	cout << a[i] <<" ";
}