#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

// [left, right)
int maximum(bool(*C)(int), int left, int right) {
    while (right - left > 1) {
        int mid = (left + right) / 2;
        (C(mid) ? left : right) = mid;
    }
    return left;
}

bool C(int x) {
    int t;
    cout << "? " << x << endl;
    cin >> t;
    return t;
}

int main() {
    cout << "! " << maximum(C, 0, 1e9 + 2) << endl;
}