import sys


def main():
    lo = 1  # lo <= ans
    hi = 10 ** 9 + 1  # hi > ans
    while lo + 1 != hi:
        mi = (lo + hi) // 2
        print(f'? {mi}')
        sys.stdout.flush()
        if input() == '1':
            lo = mi
        else:
            hi = mi
    print(f'! {lo}')
    sys.stdout.flush()


if __name__ == '__main__':
    ret = main()
    if ret is not None:
        print(ret)