//merge sort
#include <iostream>
#include <algorithm>
using namespace std;
int A[1000],B[1000],C[1000],data[1000];
int main ()
{
	int n,iA,iB,iC;
	iA=0;
	iB=0;
	iC=1;
	cin >> n;
	for(int i=0;i<=n-1;++i)
	{
		//nhap mang
		cin >> data[i];
	}
	int left, right,mid;
	left =1;
	right = n;
	mid = (left + right)/2;
	for(int i=0, j=mid ; i<=mid-1,j<=right-1 ; ++i,++j)
	{
		// tach lam 2 mang
		A[iA]=data[i];
		iA++;
		B[iB]=data[j];
		iB++;
	}


	for(int i=0;i<=mid-1;++i)
	// sap xep 2 mang
	  {
	  	for(int j=0;j<=mid-1;++j)
	  	{
	  		if(A[j]>A[j+1])
	  		{
	  			swap(A[j],A[j+1]);
			  }
			if(B[j]>B[j+1])
			{
				swap(B[j],B[j+1]);
			}
		  }
	  }
	  // in ra 2 cai mang nay da sap xep
	    for(int iA=1,iB=1;iA<=mid,iB<=right-mid;++iA,++iB)
	  	{
	  		cout << A[iA] <<' '<< B[iB] << "\n";
		  }
    for(int iA=1,iB=1;iA<=mid,iB<=right-mid;)
    {
	if(A[iA]<B[iB])
	{
		// so sanh cac phan tu A va cac phan tu B de insert vao mang C
		C[iC]=A[iA];
		iA++;
		iC++;
		if(A[iA]>B[iB])
		{
			C[iC]=B[iB];
			iB++;
			iC++;
		}
	}
}
for(int iC=1;iC<=right;++iC)
	{
		cout << C[iC] << ' ' ;
	}
}