n=int(input())
S=["a"]*n
print("?","".join(S))
t=int(input())
for i in range(n):
    for _ in range(24):
        S[i]=chr(ord(S[i])+1)
        print("?", "".join(S))
        t1=int(input())
        if t1<t:
            S[i]="a"
            break
        if t1>t:
            t=t1
            break
    else:
        t+=1
        S[i]="z"
print("!","".join(S))