l = 1
h = 10 ** 9

100.times {
    a = (l + h).div(2)
    puts "? #{a}"
    $stdout.flush
    ans = gets.to_i
    if ans == 1
        l = a
    else
        h = a - 1
    end
    
    break if l == h
}

ans = Random.rand(l..h)
puts "! #{a}"
$stdout.flush
exit