def get_password(ans):
    ret=[]
    for c in ans:
        ret.append(chr(c+ord("a")))
    return "".join(ret)
N=int(input())
ans=[0 for _ in range(N)]
i=0
while 1:
    password=get_password(ans)
    print(f"? {password}")
    match=int(input())
    if match==N:
        exit(print(f"! {password}"))
    # matchが減るなら一つ前が正解。変わらないなら繰り返す。増えたらそれが正解。
    while ans[i]<25:
        pre=match
        ans[i]+=1
        if ans[i]==25:break
        password=get_password(ans)
        print(f"? {password}")
        match=int(input())
        if match>pre:break
        elif match<pre:ans[i]-=1;match+=1;break
    if match==N:
        exit(print(f"! {password}"))
    i+=1