#!/usr/bin/env python3
import sys
l, r = 1, 10**9+1 # [l, r)
while l+1 < r:
    m = (l + r) // 2
    print('?', m)
    sys.stdout.flush()
    if int(input()): # m <= ans
        l = m
    else:
        r = m
print('!', l)