#include <bits/stdc++.h>

using namespace std;

long getVal(const vector<int>& A, int i, int j) {
    long sum = 0;
    for (int u=i;u<=j;u++) {
        for(int v=u+1;v<=j;v++) {
            if(u !=v) {
                sum+= (long)A[u]*(long)A[v];
            }
        }
    }
    
    return sum;
}
 

long largestValue(vector <int> A) {
    // Return the largest value of any of A's nonempty subarrays.
    long max = A[0]*A[1];
    for (int u=0;u<A.size();u++) {
        for(int v=u+1;v<A.size();v++) {
            long val = getVal(A,u,v);
            if (max < val) {
                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;
}