#include <bits/stdc++.h>

using namespace std;

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

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

  long long hi = numeric_limits<int>::max();
  long long lo = -1;

  int c = query(64);
  int t = 1;
  if (c <= 0) {
    for (;;) {
      c = query(0);
      if (c == 0) {
        cout << t << endl;
        return 0;
      }
      ++t;
    }
  } 

  while (hi - lo > 1) {
    long long mi = (lo + hi) / 2;
    c = query(mi - t);
    if (c > 0) lo = mi;
    else hi = mi;
    ++t;
  }
  
  cout << "! " << hi << endl;
  cout.flush();
  
  return 0;
}