N=int(input())
def get_password(ans):
    ret=[]
    for c in ans:
        ret.append(chr(c+ord("a")))
    return "".join(ret)
ans=[0 for _ in range(N)]
i=0
password=get_password(ans)
print(f"? {password}")
match=int(input())
while 1:
    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
        password=get_password(ans)
        print(f"? {password}")
        match=int(input())
        if match>pre:i+=1;break
        elif match<pre:ans[i]-=1;i+=1;break