#include <bits/stdc++.h>
using namespace std;
const int top = 1e9 + 1;
const int bottom = 1;
int main() {
	int left = bottom;
	int right = top;
	int mid;
	int result;
	while( abs(right - left) <= 1 ) {
		mid = (left + right) / 2;
		cout << "? " << mid << endl;
		cin >> result;
		if(result) left = mid;
		else right = mid;
	}
	cout << "! " << left << endl;
	return 0;
}