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

ll findProductSum(vector<ll> A, ll n)
{
    ll array_sum = 0;
    for (ll i = 0; i < n; i++)
        array_sum = array_sum + A[i];
  ll array_sum_square = array_sum * array_sum;
    ll individual_square_sum = 0;
    for (ll i = 0; i < n; i++)
        individual_square_sum += A[i]*A[i];
    return (array_sum_square - individual_square_sum)/2;
}

ll maxSubArraySum(vector<ll> a, ll size)
{
    ll max_so_far = INT_MIN, max_ending_here = 0,
       start =0, end = 0, s=0;

    for (ll i=0; i< size; i++ )
    {
        max_ending_here += a[i];

        if (max_so_far < max_ending_here)
        {
            max_so_far = max_ending_here;
            start = s;
            end = i;
        }

        if (max_ending_here < 0)
        {
            max_ending_here = 0;
            s = i + 1;
        }
    }
    vector<ll> A(end-start+1);
    ll x=0;
    for(ll k=start;k<=end;k++){
        A[x]=a[k];
       ++x;
    }
   return findProductSum( A, (end-start+1));
}

/*Driver program to test maxSubArraySum*/
int main()
{
    ll n;
    cin>>n;
    vector<ll> a(n);
    for(ll i=0;i<n;i++){
        cin>>a[i];
    }
    
    ll max_sum = maxSubArraySum(a, n);
    cout<< max_sum<<"\n";
    return 0;
}