#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int query(int x) {
  cout << "? " << x << endl;
  cout.flush();
  int ret;
  cin >> ret;
  return ret;
}

void answer(int x) {
  cout << "! " << x << endl;
  cout.flush();
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int lo = 1;
  int hi = 1e9+1;

  while (hi - lo > 1) {
    int mi = (lo + hi) / 2;
    if (query(mi))
      lo = mi;
    else
      hi = mi;
  }
  answer(lo);
  
  return 0;
}