#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>

#include<map>
#include<set>
#include<string>
#include<algorithm>
#include<functional>
using namespace std;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define INF 1<<30
#define MP make_pair
#define mp make_pair
#define pb push_back
#define PB push_back
#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define ll long long
#define ull unsigned long long

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

int main(){
cin.tie(0);
ios::sync_with_stdio(false);
	int x=ask(80);
	if(x==0){cout<<"! 80"<<endl;}
	if(x<0){
		FOR(i,2,101){
			int a = ask(0);
			if(a==0) {cout<<"! "<<i-1<<endl;return 0;}
		}
	}
	int cnt=1;
	int l=80, r = 1e9+9;
	while(r>l){
		int med=(l+r)/2;
		int ans = ask(med-cnt);
		cnt++;
		if(ans==0) { cout<<"! "<<med<<endl;return  0;}
		if(ans<0) r=med+1;
		if(ans>0) l=med;
	}
	cout<< "! "<<l<<endl;

}