#include <bits/stdc++.h> using namespace std; // #define endl "\n" #define pb push_back #define int long long #define fi first #define se second const int N = 3e5 + 5, M = 1e9 + 7, LG = 20; int n , A[N] , x; bool ch(int mid , bool o){ if (!o){ for (int i = 1 ; i<=n ; i++){ if ((i-mid) >= 1 && (i+mid) <= n){ cout << "? " << i-mid << " " << i+mid << endl; cin >> x; if (x){ return 1; } } } return 0; }else{ for (int i = 1 ; i<n ; i++){ if ((i-mid) >= 1 && (i+mid+1) <= n){ cout << "? " << i-mid << " " << i+mid+1 << endl; cin >> x; if (x){ return 1; } } } return 0; } } void solve(){ cin >> n; int l=1 , r = (n/2) + 1; while(l+1 < r){ int mid = (l+r)>>1; if (ch(mid,0)){ l = mid; }else{ r = mid; } } int ans = 2*l+1; l=0 , r = (n/2) + 1; while(l+1 < r){ int mid = (l+r)>>1; if (ch(mid,1)){ l = mid; }else{ r = mid; } } ans = max(ans , 2*l+2); cout <<"! "<< ans << endl; } signed main(){ // freopen("" , "r" , stdin); // freopen("" , "w" , stdout); // cout << setprecision(30); // ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); int ts = 1; // cin >> ts; while(ts--){ solve(); } }