// BCC
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <utility>
#include <vector>
#include <queue>

// GCC
// #include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define each(i, c) for (__typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define chmin(a, b) a = min(a, b)
#define chmax(a, b) a = max(a, b)
#define pb push_back
#define mp make_pair

typedef long long ll;

const int INF = 1 << 28;
const ll INFLL = 1ll << 56;


int main()
{
	int l = 0, r = 1e9 + 1;
	while (l + 1 < r){
		int m = (l + r) / 2;
		
		printf("? %d\n", m);
		fflush(stdout);
		
		int x;
		scanf("%d", &x);
		
		if (x) l = m;
		else r = m;
	}
	
	printf("! %d\n", l);
	fflush(stdout);
}