#include <bits/stdc++.h>
//#define DEBUG

using namespace std;

int cnt = 0;
#ifdef DEBUG
int max_num = 20;
#else
int max_num = 1000000000;
#endif
int min_num = 50;

int que(int num){
    cout << "? "  << num << endl;
    int rtn;
    cin >> rtn;
    cnt++;
    max_num--;
    min_num--;

#ifdef DEBUG
    cout << "cnt:" << cnt << endl;
    cout << "max_num:" << max_num << endl;
    cout << "min_num:" << min_num << endl;
#endif
    return rtn;
}

int main() {
    int ans;
    ans = que(50);
    if(ans != 1){
        while(true){
            ans = que(0);
            if(ans == 0){
                cout << "! " << cnt << endl;
                return 0;
            }
        }
    }
    while((max_num - min_num) > 1){
        int num = (max_num - min_num) / 2;
        ans = que(num);
        if(ans == 0){
            cout << "! " << num + cnt << endl;
            return 0;
        }
        if(ans == 1){
            min_num = num;
        }else{
            max_num = num -1;
        }
    }
    cout << "! " << min_num + cnt << endl;

    return 0;
}