def question(y):
    print(f'? {y}')
    return int(input())

def answer(y):
    print(f'! {y}')

ng = 0
ok = 10**9
while ok - ng > 1:
    x = (ok + ng) // 2
    if question(x):
        ok = x
    else:
        ng = x
answer(ok)