import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int[] counts = new int[26];
        char[] test = new char[n];
        for (int i = 0; i < 26; i++) {
            Arrays.fill(test, (char)('a' + i));
            System.out.print("? ");
            System.out.println(test);
            System.out.flush();
            counts[i] = sc.nextInt();
        }
        int acount = counts[0];
        char[] ans = new char[n];
        for (int i = 0; i < n; i++) {
            Arrays.fill(test, 'a');
            test[i] = 'b';
            System.out.print("? ");
            System.out.println(test);
            System.out.flush();
            int x = sc.nextInt();
            if (x == acount - 1) {
                ans[i] = 'a';
                counts[0]--;
                continue;
            } else if (x == acount + 1) {
                counts[1]--;
                ans[i] = 'b';
                continue;
            }
            for (int j = 2; j < 26; j++) {
                if (counts[j] == 0) {
                    continue;
                }
                test[i] = (char)('a' + j);
                System.out.print("? ");
                System.out.println(test);
                System.out.flush();
                if (sc.nextInt() == acount + 1) {
                    ans[i] = (char)('a' + j);
                    counts[j]--;
                    break;
                }
            }
        }
        System.out.print("! ");
        System.out.println(ans);
    }
    
    static String getString(long x) {
        if (x == 1) {
            return "";
        }
        if ((x - 1) % 2 == 0) {
            String current = getString((x - 1) / 2);
            if (current != null) {
                return current + "A";
            }
        }
        if ((x - 1) % 3 == 0) {
            String current = getString((x - 1) / 3);
            if (current != null) {
                return current + "B";
            }
        }
        return null;
    }
}
class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}