#include <bits/stdc++.h>

using namespace std;

void printVect(vector<vector<int>> vect){
    for(auto i : vect){
	for(auto j : i){
        	cout << j << " ";
	}
    cout << endl;
    }
    cout << endl;
}


vector<vector<int>> sub(vector<int> A){
    vector<vector<int>> v;
    for(int i=0;i<A.size();i++){
        for(int l=1;l<=A.size()-i;l++){
            vector<int> s(A.begin()+i,A.begin()+i+l);
            v.push_back(s);
        }
    }
        
    return v;
}

int value(vector<int> v){
    int sum = 0;
    if(v.size()==1)
        return v[0];
    for(int i=0;i<v.size()-1;i++){
        for(int j=i+1;j<v.size();j++){
            sum+=v[i]*v[j];
        }
    }
    return sum;
}

long largestValue(vector <int> A) {
    vector<vector<int>> subArrays = sub(A);
    //printVect(subArrays);
    int max = -1000000;
    int val;
    for(auto v:subArrays){
        val = value(v);
        //cout << "val: " << val << endl;
        if(val > max)
            max = val;
    }
    return max;
}

int main() {
    int n;
    cin >> n;
    vector<int> A(n);
    for(int A_i = 0; A_i < n; A_i++){
       cin >> A[A_i];
    }
    long result = largestValue(A);
    cout << result << endl;
    return 0;
}