n=int(input())
s=""
for i in range(n):
	g=[]
	for j in range(25):
		print("?","a"*i+chr(j+ord("a"))+"a"*(n-i-1))
		g+=[int(input())]
	g+=[min(g)+1]
	for j in range(26):
		if g[j]==max(g):
			s+=chr(j+ord("a"))
			break
print("!",s)