#include <cstdio>
#include <cstdlib>
#include <cstddef>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <iostream>
#include <iomanip>
#define L64 long long
#define MOD (1000000007LL)

int main(void)
{
  int min = 1;
  int max = 1000000000;
  int ret = 0;
  while(min != max){
    int mid = (min + max + 1) / 2;
    std::cout << "? " << mid << std::endl << std::flush;
    std::cin >> ret;
    if(ret == 1){
      min = mid;
    } else {
      max = mid - 1;
    }
  }
  std::cout << "! " << min << std::endl << std::flush;
}