#include <iostream>
#include <vector>
#define C main
#define D push_back
#define E size
using namespace std;
typedef vector<int> v; typedef int u;
void A(int&a,int&b){int c=a;a=b;b=c;}
void B(vector<int>& a){ for(u b=0;b<=a.E();b++) {
int c=b;for(u d=b+1;d<a.size();d++)if(a[d]<a[c])c
=d;A(a[b],a[c]); } } int C(){ v a; int b; cin>>b;
while(cin){ a.D(b); cin >> b; } B(a); for (u c=0; 
c<a.E()*2;c++)cout<<a[c]<<" "; cout<<endl; delete 
&a;}