import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int p = 1;
    int l = 0;
    int r = (int)Math.pow(10, 9) + 1;
    int ans = 0;
    System.out.println("? " + 99);
    System.out.flush();
    int res = sc.nextInt();
    if(res == -1) {
      for(int i = 0; i < 99; i++) {
        System.out.println("? " + 0);
        System.out.flush();
        int t = sc.nextInt();
        if(t == 0) {
          ans = p; 
        }
        p++;
      }
    } else {
      while(l < r) {
        int med = (l + r) / 2;
        System.out.println("? " + med);
        System.out.flush();
        int t = sc.nextInt();
        if(t == -1) {
          r = med - 1;
          ans = l + p;
          l--;
        } else if(t == 1) {
          l = med;
          ans = l + 1 + p;
          r--;
        } else {
          ans = med + p;
          break;
        }
        p++;
      }
    }
    System.out.println("! " + ans);
    System.out.flush();
  }
}