/* -*- coding: utf-8 -*-
 *
 * 2768.cc:  No.2768 Password Crack - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 100;

/* typedef */

/* global variables */

char s[MAX_N + 4];

/* subroutines */

int query(char s[]) {
  printf("? %s\n", s); fflush(stdout);

  int r;
  scanf("%d", &r);
  return r;
}

/* main */

int main() {
  int n;
  scanf("%d", &n);

  fill(s, s + n, 'a');
  int an = query(s);

  if (an < n) {
    for (int i = 0; i < n; i++) {
      char c = 'b';
      for (; c < 'z'; c++) {
	s[i] = c;
	int r = query(s);
	if (r < i + an) { c = 'a'; break; }
	if (r > i + an) break;
      }
      s[i] = c;
      if (c == 'a') an--;
    }
  }

  printf("! %s\n", s); fflush(stdout);
  //for (int i = 0; i < 1000000000; i++);
  
  return 0;
}