import math._

object Main {
  def main(args: Array[String]) {
    val sc = new java.util.Scanner(System.in)

    var ans = 0
    var lo = 0
    var hi = 1000000000
    while (lo <= hi) {
      val m = (lo + hi) / 2
      println(s"? ${m}")

      val n = sc.nextInt
      n match {
        case 0 => hi = m - 1
        case 1 => {
          ans = m
          lo = m + 1
        }
      }
    }
    println(s"! ${ans}")
  }
}