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

ll largestValue(vector <ll> A) {
    // Return the largest value of any of A's nonempty subarrays.
  vector<ll> xx(A.size()+2,0);
  for(ll i=1;i<=A.size();i++) xx[i]=xx[i-1]+A[i-1];
  vector<ll> yy(A.size()+2,0);
  for(ll i=1;i<=A.size();i++) yy[i]=yy[i-1]+A[i-1]*A[i-1];
  ll ans=0;
  for(ll i=1;i<=A.size();i++){
    for(ll j=i+1;j<=A.size();j++){
      ll x=xx[j]-xx[i-1];
      x=x*x;
      ll y=yy[j]-yy[i-1];
      ll p=x-y;
      p=p/2;
      ans=max(ans, p);
      //cout<<x<<" "<<y<<" ";
      //cout<<ans<<" "<<p<<endl;
    }
  }
  return ans;
}

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