ok=10
ng=10**9+10

print(f'? {100}',flush=True)
f=int(input())
if f == -1:
    ok = 9
    ng = 100


    for i in range(9):
        mid=(ok+ng)
        print(f'? {mid-i}',flush=True)
        t=int(input())
        if t >= 0:
            ok = mid
        else:
            ng = mid
            
    print(f'! {ok+1}')


else:

    for  i in range(1,100):
        mid=(ok+ng)//2
        t= max(mid-i,0)
        print(f'? {t}',flush=True)
        t=int(input())
        if t >= 0:
            ok = mid
        else:
            ng = mid

    print(f'! {ok}')