#include <iostream>

#define questionMAX 100

/*
answer = true  := 以上
answer = false := 未満
*/

class REALM
{
	public:
	
	unsigned long long N_MAX, N_MIN, N_MEAN;
	
	void getMean(void)
	{
		N_MEAN = (N_MAX + N_MIN) / 2;
	}
};

bool question(int x)
{
	bool answer;
	
	std::cout << "? " << x << std::endl;
	
	std::cin >> answer;
	
	if(answer)
	{
		return true;
	}
	else
	{
		return false;
	}
}

REALM getRealm(REALM realm_prev, bool answer)
{
	REALM realm_next;
	
	
}

int main(void)
{
	REALM realm;
	realm.N_MAX = 1000000000;
	realm.N_MIN = 1;
	realm.getMean();
	
	for(int i = 0; i < questionMAX; i ++)
	{
		if(question(realm.N_MEAN))
		{
			realm.N_MIN = realm.N_MEAN;
			realm.getMean();
		}
		else
		{
			realm.N_MAX = realm.N_MEAN - 1;
			realm.getMean();
		}
		
		if(realm.N_MAX == realm.N_MIN)
		{
			std::cout << "! " << realm.N_MAX << std::endl << std::flush;
			break;
		}
		else if(realm.N_MIN == realm.N_MAX - 1)
		{
			if(question(realm.N_MAX))
			{
				std::cout << "! " << realm.N_MAX << std::endl << std::flush;
				break;
			}
			else
			{
				std::cout << "! " << realm.N_MIN << std::endl << std::flush;
				break;
			}
		}
		
		//for debug
		//std::cout << realm.N_MIN << " <= x <= " << realm.N_MAX << std::endl;
	}

	return 0;
}