#include <bits/stdc++.h> using namespace std; #define print(l) for(auto i:l) cout<<i<<" ";cout<<endl; #define input(t,l,n) vector<t>l(n);for(int i = 0;i<n;i++)cin>>l[i]; #define int long long #define pb push_back #define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> #define all(l) l.begin(),l.end() #define pii pair<int,int> #define fi first #define se second const int M = 1e9+7; const int inf = 1e18; int bp(int x, int y, int p){ int res = 1; x = x % p; while (y > 0) { if (y & 1) res = (res * x) % p; y = y >> 1; x = (x * x) % p; } return res; } int MI(int n, int p){ return bp(n, p - 2, p); } int mul(int x,int y, int p){ return x * 1ull * y % p; } int di(int x,int y, int p){ return mul(x, MI(y, p), p); } int n , m , k , q; // string s; map<pair<int,int>,int>qur; int ask(int l,int r){ // if(qur[{l,r}] == 1){ // return 1; // } // else if(qur[{l,r}] == 2){ // return 0; // } // else{ if(k == 200000){ while(1){ k++; } } cout<<"? "<<l<<" "<<r<<endl; int re; cin>>re; k++; // qur[{l,r}] = re+(re == 0); // // update(l,r,re); return re; // } } void solve(int testcase_number){ cin>>n; int flen = 1; // if l is odd vector<int>odd; for(int i = 1;i<=n;i+=2){ odd.pb(i); } // print(odd); int l = 0; int r = odd.size(); while(r-l >1){ int m = (l+r)/2; int len = odd[m]; int f = 0; int ans =0 ; for(int i = 1;i+len-1<=n;i++){ ans = ask(i,i+len-1); if(ans){ f = 1; break; } } if(f){ l = m; } else{ r = m; } } if(l != -1) flen = max(flen,odd[l]); // if l is even vector<int>even = {1}; for(int i = 2;i<=n;i+=2){ even.pb(i); } // print(even); l = 0; r = even.size(); while(r-l > 1){ int m = (l+r)/2; int len = even[m]; int f = 0; int ans =0 ; for(int i = 1;i+len-1<=n;i++){ ans = ask(i,i+len-1); if(ans){ f = 1; break; } } if(f){ l = m; } else{ r = m; } } if(l!= -1)flen = max(flen,even[l]); cout<<"! "<<flen<<endl; // evve } signed main(){ // ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE // cin.tie(0), cout.tie(0); // cout << fixed<<setprecision(9); int t = 1; // cin>>t; for(int i = 1;i<=t;i++){ solve(i); } }