#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

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