// g++ -std=c++11 -O3 -fmax-errors=1
#include <bits/stdc++.h>
using namespace std;
#define int ll
typedef long long ll;
typedef long double dbl;
typedef pair<int,int> pii;
typedef vector<int> vi;

#define X first
#define Y second
#define mp make_pair
#define pb push_back
#define all(c) begin(c), end(c)
#define mem(c,v) memset(c, v, sizeof c)
#define uni(c) c.resize(distance(c.begin(), unique(all(c))))

#define rep(i,n) for(ll i=0, _n=(n); i<_n; i++)
#define rep1(i,n) for(ll i=1, _n=(n); i<=_n; i++)
#define cout(d) cout << fixed << setprecision(d)
#define err(x) cerr << #x << " = " << x << "\n"

#define cases int _t_; cin >> _t_; rep1(_t,_t_)
#define coutt cout << "Case " << _t << ": "
#define io ios_base::sync_with_stdio (false); cin.tie(NULL);

const dbl eps=1e-12, pi=acosl(-1);
const ll inf=1e16, mod=1e9+7;
const int N=2e6+10;

int a[N];

#undef int
int main() {
#define int ll

	int n; cin >> n;
    rep(i,n) cin >> a[i];
    int ans=0; rep(i,n) {
        int s1=0, s2=0, j=i;
        while(j<n) {
            s1+=a[j];
            s2+=a[j]*a[j];
            ans=max(ans, s1*s1-s2);
            j++;
        }
    }
    cout << ans/2;
    return 0;
}