#include<bits/stdc++.h>
using namespace std;
int main()
{
  cout << "? 0" << endl;
  int X_abs; cin >> X_abs;
  cout << "? " << X_abs << endl;
  int diff; cin >> diff;
  cout << "! " << ( diff == 0 ? X_abs : -X_abs ) << endl;
}