#include <bits/stdc++.h> using namespace std; using i64 = long long; template<typename T> using vec = vector<T>; int last1 = 0,last2 = 0,c = INT_MAX; int query(int sorgu){ if (last1 == 0) last1 = sorgu; else { last2 = last1; last1 = sorgu; } cout << "? " << sorgu << endl; cout.flush(); int q; cin >> q; if (q && last2 != 0) c = min(c,abs(last1 - last2)); return q; } int main(){ ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); int n; cin >> n; query(n / 2); bool ok = query(1); if (ok == 1){ query(n / 2 - 1); for (int i = 2; i < n / 2; i++){ query(i); query(n / 2 - i); } } else { query(n); for (int i = 2; i < n / 2; i++){ query(i); query(n - i + 1); } } cout << "= " << c << endl; cout.flush(); return 0; }