histogramarea(stack)

#include<bits/stdc++.h>
using namespace std;
#define int long long int

int area(int *arr,int n){

    stack<int> s;

    int top;
    int mx=INT_MIN;
    int area;

    int i=0;
    while(i<n){

        if(s.empty() || arr[s.top()] < arr[i]){
            s.push(i);
            i++;
        }
        else{
            top=s.top();
            s.pop();

            if(s.empty()) area = arr[top]*i;

            else area = arr[top]*(i-s.top()-1);

            mx=max(area,mx);

        }
    }

    while(!s.empty()){
        top=s.top();
        s.pop();

        if(s.empty()) area = arr[top]*i;

        else{
            area = arr[top]*(i-s.top()-1);
        }

        mx=max(mx,area);

    }

    return mx;

}

int32_t main() {

    #ifndef ONLINE_JUDGE
    // for getting input from input.txt
    freopen("input.txt", "r", stdin);
    // for writing output to output.txt
    freopen("output.txt", "w", stdout);
    #endif

    int n;
    cin >> n;

    int arr[n];

    for(int i=0;i<n;i++){
        cin >> arr[i];
    }

    cout << area(arr,n) << endl;


    return 0;
}