I,R,O=input,range,print
N=int(I())
S=""
T="a"*N
O("?",T)
n=int(I())
a=0
for i in R(N):
	for d in R(1,25+(i<N-1)):
		c=chr(ord('a')+d)
		O("?",T[:i]+c+T[i+1:])
		m=int(I())
		if m>n:S+=c;break
	else:S+="za"[i<N-1or a<n];a+=1
O("!",S)