#include using namespace std; constexpr int Inf = 1000000010; constexpr long long INF= 2000000000000000000; template inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; } template T modpow(T N, U P, T M = -1) { if(P < 0) return 0; T ret = 1; if(M != -1) ret %= M; while(P) { if(P & 1) { if(M == -1) ret *= N; else ret = ret * N % M; } P /= 2; if(M == -1) N *= N; else N = N * N % M; } return ret; } constexpr long long MOD = 998244353; int main() { int n; cin >> n; for(int i = 0;i < n;i += 2) { cout << "? " << i << " " << i + 1 << endl; int a; cin >> a; if(a == i) { cout << "! " << i + 1 << endl; return 0; } else { cout << "! " << i << endl; return 0; } } cout << "! " << n - 1 << endl; }