#include <iostream>

using namespace std;

int main() {
	// [lower, upper)
	int lower = 1;
	int upper = 1000000001;
	while (lower + 1 != upper) {
		int middle = (lower + upper) / 2;
		cout << "? " << middle << endl << flush;
		int yes;
		cin >> yes;
		if (yes) {
			lower = middle;
		} else {
			upper = middle;
		}
	}
	cout << "! " << lower << endl << flush;
	return 0;
}