#include <iostream>

using namespace std;

int main()
{
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int N, i, cur, n;
    char T[101];
    cin >> N;
    for (i = 0; i != N; ++i) T[i] = 'a';
    T[N] = '\0';

    cout << "? " << T << '\n' << flush;
    cin >> cur;
    for (i = 0; i != N; ++i)
    {
        T[i] = 'b';
        cout << "? " << T << '\n' << flush;
        cin >> n;
        if (n == cur)
            for (T[i] = 'c'; T[i] != 'z'; ++T[i])
            {
                cout << "? " << T << '\n' << flush;
                cin >> n;
                if (n != cur)
                {
                    cur = n;
                    break;
                }
            }
        else if (n < cur) T[i] = 'a';
        else cur = n;
    }

    cout << "! " << T << '\n';
    return 0;
}