#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(int i = (n) - 1; (i) >= 0; --i)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD LL(1e9 + 7)
#define INF 1000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;

int main() {
	int l = 1;
	int r = 1e9;
	int ans = (l + r) / 2;
	int rea;
	int cnt = 1;
	while (cnt != 99) {
		cout << "? " << ans << endl;
		cin >> rea;
		if (rea)
			l = ans;
		else
			r = ans;
		ans = (l + r) / 2;
		cnt++;
	}
	cout << "! " << ans << endl;
	return 0;
}