#include<bits/stdc++.h>
using namespace std;
int n , q , atmp;
string s[10005] , ans[10005];
char c; 
bool flag[10005];
bool cmp(string l , string r)
{
	int q = min(l.size() , r.size());
	for(int i = 0 ; i < q ; i++)
	{
		if(l[i] < r[i])
		{
			return 1;
		}
		if(l[i] > r[i])
		{
			return 0;
		}
	}
	return 1;
}
int main()
{
	ios::sync_with_stdio(0);
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin >> n;
	for(int i = 1 ; i <= n ; i++)
	{
		cin >> s[i];
		q += s[i].size();
	}
	q = q / (n / 2);
	cin >> c;
	sort(s + 1 , s + n + 1 , cmp);
	for(int i = 1 ; i <= n ; i++)
	{
		if(flag[i])
		{
			continue;
		}
		flag[i] = 1;
		for(int j = 1 ; j <= n ; j++)
		{
			if(flag[j])
			{
				continue;
			}
			if(s[i].size() + s[j].size() == q)
			{
				atmp++;
				if(cmp(s[i] + c + s[j] , s[j] + c + s[i]))
				{
					ans[atmp] = s[i] + c + s[j] + '\n'; 
				}
				else
				{
					ans[atmp] = s[j] + c + s[i] + '\n';
				}
				flag[j] = 1;
				break;
			}
		}
	}
	sort(ans + 1 , ans + atmp + 1 , cmp);
	for(int i = 1 ; i <= atmp ; i++)
	{
		cout << ans[i];
	}
	return 0;
}

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