#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;
int main()
{
	int n;
	cin >> n;
	string ans(n, 'a');
	for (int i = 0; i < n; ++i)
	{
		int bs;
		cout << "? " << ans << endl;
		cin >> bs;
		for (char j = 'b'; j <= 'z'; ++j)
		{
			ans[i] = j;
			if (j == 'z') break;
			cout << "? " << ans << endl;
			int tmp;
			cin >> tmp;
			if (bs > tmp)
			{
				ans[i] = 'a';
				break;
			}
			else if (bs < tmp) break;
		}
	}
	cout << "! " << ans << endl;
}