// #pragma optimize ("g",on)
// #pragma GCC optimize ("inline")
// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC optimize ("03")
#include <bits/stdc++.h>
#define pb push_back
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
// #define int long long
#define all(v) v.begin(),v.end()
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 5e4 + 1, inf = 1e9, mod = 998244353;
int ask(int l, int r){
cout << "? " << l << ' ' << r << endl;
int res;
cin >> res;
return res;
}
void solve(){
int n;
cin >> n;
int sz = 2, i = 1;
int ans = 0;
while(i + sz - 1 <= n){
if(ask(i, i + sz - 1)){
ans = sz;
sz += 2;
if(i != 1) i--;
continue;
}
else{
i++;
}
}
sz = max(3, ans + 1);
i = 1;
while(i + sz - 1 <= n){
if(ask(i, i + sz - 1)){
ans = sz;
sz += 2;
if(i != 1) i--;
continue;
}
else{
i++;
}
}
cout << "! " << ans << endl;
/*
aabca
*/
}
signed main(){
SS
// freopen("trains.in", "r", stdin);
// freopen("trains.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
