#include<iostream>

int main() {
	int max = 1e9, min = 1, mid;

	while(true){
		mid = (max + min) / 2;
		std::cout << "? " << mid << std::endl;
		int ans;
		std::cin >> ans;
		if (ans == 1) {
			min = mid;
		} else {
			max = mid;
		}
		if (min + 1 == max) break;
	}
	std::cout << "! " << min << std::endl;
	return 0;
}