lo = 1
hi = 10 ** 9
ans = lo
while lo <= hi:
    m = (lo + hi) // 2
    print(f'? {m}')
    r = int(input())
    if r == 0:
        hi = m - 1
    else:
        lo = m + 1
        ans = max(ans, m)

print(f'! {ans}')