#include <bits/stdc++.h> using namespace std; int main() { long long int n; cin >> n; long long int l = 1, r = n - 1, h = 0, fl = 1, res; while (l <= r) { long long int mid = (l + r) >> 1; h += mid * fl; fl *= -1; if (mid <= n - 1) l = mid + 1; else r = mid - 1; } if (h > 0) h = n - h; else h = 1 - h; fl = 1; l = 1; r = n - 1; cout << "? " << h << endl; char x; cin >> x; while (l <= r) { long long int mid = (l + r) >> 1; h += fl * mid; fl *= -1; cout << "? " << h << endl; char x; cin >> x; if (x == '1') { res = mid; r = mid - 1; } else l = mid + 1; } cout << "! " << res << endl; }