from random import shuffle
N = int(input())
l = list("abcdefghijklmnopqrstuvwxyz")
S = ""
for i in range(N):
	shuffle(l)
	cnts = []
	c1 = set()
	for c in l:
		print('?', S + c + 'a' * (N - 1 - i))
		x = int(input())
		cnts.append((x, c))
		c1.add(x)
		if len(cnts) >= 3 and len(c1) == 2:
			cnts.sort()
			c = 0
			for i, _ in cnts:
				if i == cnts[0][0]:
					c += 1
			if c == 1:
				S += cnts[0][1]
			else:
				S += cnts[-1][1]
			break
print('!', S)