#include<bits/stdc++.h>
#define Yukinoshita namespace
#define Yukino std
#define int long long
using Yukinoshita Yukino;
int read()
{
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9') w=ch=='-'?-1:1,ch=getchar();
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
mt19937_64 randomEngine(time(0));
long long random(long long l,long long r)
{
	r--;
    uniform_int_distribution<long long> distribution(l,r);
    return distribution(randomEngine);
}
signed main()
{
	vector<int> vc;
	int qwq=1e18;
	qwq--;
	for(int i=0;i<41;i++,qwq/=2)
		vc.push_back(qwq);
	sort(vc.begin(),vc.end());
	int g=0;
	for(auto x:vc)
	{
		cout<<"? "<<x<<endl;
		fflush(stdout);
		int k;
		cin>>k;
		g=__gcd(g,x-k);
	}
	cout<<"! "<<g<<endl;
	fflush(stdout);
}