#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include<utility>
using namespace std;
int getsum(vector<int>v,int start,int end){
    int sum=0;
    vector<pair<int,int> >p;
    for(int i=start;i<=end-1;i++){
        for(int j=i+1;j<end;j++){
            p.push_back(make_pair(v[i],v[j]));
        }
    }
   // cout<<"size is: "<<p.size();
    for(int i=0;i<p.size();i++){
    	//cout<<"sum got infinite\n";
        sum=sum+(p[i].first*p[i].second);
    }
    return sum;
}

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    cin>>n;
    vector<int>v(n);
    for(int i=0;i<n;i++){
        cin>>v[i];
    }
    int max=-9999;
    int temp=0;
    for(int i=0;i<n;i++){
        for(int j=i+1;j<n;j++){
            temp=getsum(v,i,j);
            if(temp>max){
                max=temp;
            }
        }
    }
    cout<<max;
    return 0;
}