import java.util.*;

public class Exercise90{
  public static void main (String[] args){

    Scanner sc = new Scanner(System.in);

    int head = 1;
    int tail = 1000000000;
    int center = 0;
    while(true){
      center = (tail - head) / 2 + head;
      if(tail - head < 2){
        break;
      }
      System.out.println("? " + center);
      System.out.flush();

      int answer = sc.nextInt();
      
      if(answer == 0){
        tail = center;
      }else{
        head = center;
      }
    }
    System.out.println("! " + center);
  }
}