#include<bits/stdc++.h>
using lint=long long;
bool query(lint x){
    std::cout<<"? "<<x<<std::endl;
    std::cin>>x;
    return x;
}
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    lint yes=0,no=1'000'000'001;
    while(no-yes>1){
        lint c=(yes+no)/2;
        (query(c)?yes:no)=c;
    }
    std::cout<<"! "<<yes<<std::endl;
}