Test case issue [Histogram]

[aburifat]

Please provide the information below:

1. Problem Link: https://lightoj.com/problem/histogram
2. Your concern, describe the issue: Weak dataset. The judge accepted the code which didn't provide an entirely correct answer.
3. Your code or submission link: https://lightoj.com/submission/2315348

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MX 30030
ll arr[MX];
int main(){
	ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	ll t=1;
	cin>>t;
	for(ll T=1;T<=t;T++){
		ll ans=0;
		ll n;
		cin>>n;
		for(ll i=0;i<n;i++){
			cin>>arr[i];
		}
		stack<ll>st;
		ll left[MX],right[MX];
		for(ll i=0;i<n;i++){
			while(!st.empty()){
				if(arr[st.top()]>=arr[i])st.pop();
				else break;
			}
			if(st.empty()){
				left[i]=0;
			}else{
				left[i]=(st.top())+1;
			}
			st.push(i);
		}
		while(!st.empty())st.pop();
		for(ll i=n-1;i>=0;i--){
			while(!st.empty()){
				if(arr[st.top()]>=arr[i])st.pop();
				else break;
			}
			if(st.empty()){
				right[i]=n-1;
			}else{
				right[i]=(st.top())-1;
			}
			st.push(i);
		}
		for(ll i=0;i<n-1;i++){
			ll val=abs(right[i]-left[i])+1;
			val*=arr[i];
			ans=max(ans,val);
		}
		cout<<"Case "<<T<<": "<<ans<<endl;
	}
	return 0;
}

5. Test case content: The test case for which this code fails to give the correct answer:

Input:
1
1
1

Expected Output:
Case 1: 1

Code Output:
Case 1: 0