#include <iostream>
using namespace std;
using ll = unsigned long long;
int main()
{
	ll lb = 0, ub = (ll)(1e9+1);
	for ( int i = 0; i < 100; ++ i ) {
		if ( ub - lb < 2 ) break;

		ll const mid = lb + (ub - lb) / 2;
		cout << "? " << mid << endl;

		int cond;
		cin >> cond;
		(cond != 0 ? lb : ub) = mid;
	}
	cout << "! " << lb << endl;
	return 0;
}