#ifdef __AVX2__ #pragma GCC target "avx2" #endif #pragma GCC optimize "O3" #pragma GCC optimize "unroll-loops" #include <bits/stdc++.h> #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> using namespace __gnu_pbds; using namespace std; #define int long long #define elif else if #define all(l) begin(l),end(l) #define rall(l) rbegin(l),rend(l) #define append push_back #define print(l) for(auto i:l) cout<<i<<' '; cout<<endl; #define pprint(a,b) cout<<a<<' '<<b<<endl; #define inp(l) for(auto &i:l) cin>>i; #define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> #define pai make_pair // #define endl "\n" #define pii pair<int,int> #define fi first #define se second #define vec vector // const int mod=998244353; const int mod1=998244353; const int mod=1e9+7; const int N=2e5+5; // string s; // bool qu(int l,int r){ // string a; // for(int i=l-1;i<=r-1;i++) a+=s[i]; // string b=a; // reverse(all(b)); // return a==b; // } int iter=1,itera=1; void solve(){ int n; cin>>n; // cin>>s; int ans=0; for(int i=1;i<=n;i++){ while(1){ int l,r; int x=ans+2; if(x%2){ l=i-x/2; r=i+x/2; } else{ l=i-x/2+1; r=i+x/2; } if(l<1 or r>n) break; cout<<"? "<<l<<' '<<r<<endl; int f; // f=qu(l,r); cin>>f; // cout<<l<<' '<<r<<' '<<f<<endl; if(f) ans=x; else break; } } int ans1=1; for(int i=1;i<=n;i++){ while(1){ int l,r; int x=ans1+2; if(x%2){ l=i-x/2; r=i+x/2; } else{ l=i-x/2+1; r=i+x/2; } if(l<1 or r>n) break; cout<<"? "<<l<<' '<<r<<endl; int f; cin>>f; // f=qu(l,r); // cout<<l<<' '<<r<<' '<<f<<endl; if(f) ans1=x; else break; } } // cout<<"ans "<<ans<<' '<<ans1<<endl; cout<<"! "<<max(ans,ans1)<<endl; } signed main(){ // freopen("","r",stdin); // freopen("","w",stdout); ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); cout<<fixed<<setprecision(20); // cin>>itera; for(iter=1;iter<=itera;iter++) solve(); }