#include <iostream>
#include <map>
using namespace std;
int main(void)
{
  int n, head, tail, prev;
  map<int, int> memo;

  head = 1, tail = 1000000000, prev = (head + tail) / 2;
  while(head != tail){
    int mid = (head + tail) / 2;
    cout << "? " << mid << endl;
    cin >> n;
    if(n) head = mid;
    else tail = mid;

    memo[mid]++;
    // if(mid == 1 || mid == 1000000000 || (memo[mid] && !memo[mid-1])){
    //   cout << "! " << mid << endl;
    //   break;
    // }


    // if((head + tail) / 2 == prev){
    //   cout << "! " << mid << endl;
    //   break;
    // }
    // prev = mid;

    if(memo[mid] >= 3){
      cout << "! " << head << endl;
      break;
    }
  }
}