lower = 0
upper = 10**9 + 1
mid = 200
n_query = 0
while lower + 1 < upper:
    n_query += 1
    print('? {}'.format(mid), flush=True)
    ans = int(input())
    if ans == 0:
        print('! {}'.format(mid + n_query), flush=True)
        break
    if ans == 1:
        lower = mid
        upper -= 1
    if ans == -1:
        upper = mid - 1
        lower = max(0, lower - 1)
    mid = (lower + upper) // 2
else:
    print('! {}'.format(lower + n_query), flush=True)