#include<bits/stdc++.h>
using namespace std;
int result(vector<int> &arr)
{
    int n=arr.size();
    stack<int> st;
    int area=0;
    for(int i=0;i<=n;i++)
    {
        while(!st.empty()&&(i==n)||arr[st.top()]>=arr[i])
        {
            int height=arr[st.top()];
            st.pop();
            int width;
            if(st.empty())
            width=i;
            else
            width=i-st.top()-1;
            area=max(area,height*width;)
        }
        
        st.push(i);
    }
    return area;
}
int main()
{
    vector<int> arr={2,1,5,6,2,3,1};
    cout<<result(ans);
}