#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<functional>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
using namespace std;

int ask(int Y){
	cout << "? " << Y << endl;
	int res;
	cin >> res;
	return res;
}

signed main() {
	int st = 50, ed = 1000000000, medi;
	int counter = 0;
	
	if (ask(50) <= 0) {
		for (int i = 0; i <= 50; i++) {
			if (ask(0) == 0) {
				cout << "! " << i + 1 << endl;
				break;
			}
		}
		return 0;
	}
	
	while (st <= ed) {
		medi = (st + ed) / 2;
		int res = ask(medi - counter);
		if (res == 0)
			break;
		if (res == -1)
			ed = medi - 1;
		if (res == 1)
			st = medi + 1;
		counter++;
	}
	cout << "! " << medi + 1 << endl;
	return 0;
}