from sys import stdin, stdout input = lambda: stdin.readline().rstrip() write = stdout.write def main(): min_ = 1 max_ = 1000000000 mid = max_ // 2 while 1: print('?', mid) stdout.flush() res = int(input()) if res: min_ = mid else: max_ = mid - 1 n = max_ - min_ if n < 2: break else: mid = min_ + n // 2 print(min_) stdout.flush() main()