#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
#include<immintrin.h>
using namespace std;
bool ok(long long int mid){
	cout << "?" << " " << mid << endl;
	int ind;
	cin >> ind;
	return ind;
}
int main(){
	long long int mint = 0;
	long long int maxt = INT_MAX;
	while (mint + 1LL < maxt){
		long long int mid = (mint + maxt) >> 1;
		if (ok(mid)){
			mint = mid;
		}
		else{
			maxt = mid;
		}
	}
	if (mint != maxt){
		if (ok(mint)){
			maxt = mint;
		}
		else{
			mint = maxt;
		}
	}
	cout << "!" << " " << mint << endl;
	return 0;
}