#include <bits/stdc++.h>

using namespace std;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

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

void answer(int n){
    std::cout << "! " << n << std::endl;
}

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    // if minimizing, lb satisfies lb > ub
    // if maximizing, lb satisfies lb < ub
    int64_t lb = 1, ub = 1001001001;

    while(std::abs(ub - lb) > 1){
        int64_t mid = (lb + ub) / 2;

        if(ask(mid) == 1){
            lb = mid;
        }else{
            ub = mid;
        }
    }

    answer(lb);
}