ok=10
ng=10**9+10
for  i in range(100):
    mid=(ok+ng)//2
    t=max(mid-i,10)
    
    print(f'? {t}',flush=True)
    t=int(input())
    if t == 10:
        ok = 10
        continue
    if t >= 0:
        ok = mid
    else:
        ng = mid

print(f'! {max(ok,10)}')