N=int(input())

def ans(a):
    print(f'! {a}')

def get(a):
    print(f'? {a}')
    k=int(input())
    return k

now=['a']*N
for i in range(N):
    first=get(''.join(now))
    for k in range(1,25):
        now[i]=chr(ord('a')+k)
        res=get(''.join(now))
        if res>first:
            break
    else:
        if first==res:
            now[i]='z'
        else:
            now[i]='a'

ans(''.join(now))