#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ll long long
#define ld long double
#define forn(i,j) for(ll i = 0; i < j; i++)
#define forrange(i,j,k) for(int i = j; i < k; ++i)
#define rof(i,j) rof(int i = j; i >= 0; --i)
#define pii pair<int,int>
#define vll vector<ll>
#define vi vector<int>
#define vvll vector<vll>
#define vvi vector<vi>
#define vb vector<bool>
#define pb push_back
#define p push
#define f first
#define s second
#define all(x) x.begin(), x.end()
#define eb emplace_back
#define debug(x) cerr << #x << " is " << x << endl;
#define MOD 1000000007
int t;
bool check(int l,int r){
if(l<1 or r>n)return false;
cout << "? " << l << ' ' << r << endl;
int a;cin>>a;
return a==1;
}
int main(){
int n;
cin >> n;
int mtx = 0;
forrange(i,1,n+1){
if(i + mtx + 1 < n + 1 && i - mtx - 1 > 0){
if(check(i - mtx - 1,i + mtx + 1)){
mtx++;
}
}
}
if(mtx == 0){
cout << "!" << 1 << endl;
}
else{
cout << "!" << mtx << endl;
}
}
Compilation message
Main.cpp: In function 'bool check(int, int)':
Main.cpp:30:17: error: 'n' was not declared in this scope
30 | if(l<1 or r>n)return false;
| ^
