#include <iostream>
using namespace std;
#include <map>
#include <list>

int n, len;
bool cod;
char value;
string s, sm = "", ss = "";
map<char, int> mmp;
list<char> lst;

int main()
{
	cin >> n >> s;

	len = n / 2;
	for (int i = 0; i < n; ++i)
	{
		++mmp[s[i]];
		lst.push_back(s[i]);
	}
	while (n--)
	{
		if (!cod)
		{
			value = lst.back();
			sm += value;
			lst.pop_back();
		}
		else
		{
			value = mmp.begin()->first;
			ss += value;
			lst.remove(value);
		}
		mmp[value] > 1 ? --mmp[value] : mmp.erase(value);
		cod = !cod;
	}

	if (sm == ss)
		cout << "NE" << "\n";
	else
	{
		for (int i = 0; i < len; ++i)
		{
			if (sm[i] < ss[i])
			{
				cout << "NE" << "\n"
					 << ss;
				return 0;
			}
		}
		cout << "DA" << "\n";
	}
	cout << ss;

	return 0;
}

束手无策了