#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;

    int C = min(8 * n, 5000);

    // 选择最优的m，使得剩余硬币数乘以(m+1)最大
    double max_f = 0;
    int best_m = 1;
    int max_possible_m = (int)sqrt(C);
    for (int m_candidate = 1; m_candidate <= max_possible_m; ++m_candidate) {
        int cost = m_candidate * m_candidate;
        if (cost > C)
            continue;
        int remaining = C - cost;
        double current_f = (double)remaining * (m_candidate + 1) / (2.0 * n);
        if (current_f > max_f || (current_f == max_f && m_candidate > best_m)) {
            max_f = current_f;
            best_m = m_candidate;
        }
    }

    int m = best_m;
    cout << "! " << m << endl;
    cout.flush();

    int remaining_coins = C - m * m;
    int max_guess = 0;

    for (int i = 0; i < remaining_coins; ++i) {
        cout << "? 1" << endl;
        cout.flush();

        int current_max;
        cin >> current_max;

        if (current_max == -1) {
            return 0;
        }

        if (current_max > max_guess) {
            max_guess = current_max;
        }
    }

    cout << "! " << max_guess << endl;
    cout.flush();

    return 0;
}