#include <bits/stdc++.h>
using namespace std;
#define FOR(i, x, y) for(ll i = (x); i <= (y); ++i)
#define bug(a) cout << #a << " = " << a << endl;
#define fbug(a, x, y) { cout << #a << ": "; FOR(i, x, y) cout << a[i] << ' '; cout << endl; }
#define pb push_back
#define mp make_pair
#define endd "\n"
#define fast ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define input freopen("inp.txt","r",stdin)
#define output freopen("out1.txt","w",stdout)
#define loop(i,n) for(ll i=0;i<n;i++)
#define rloop(i,n) for(ll i=n-1;i>=0;i--)
#define ll long long
#define Z size()
#define pii pair<int,int>
#define pll pair<ll,ll>
#define setp(x) fixed<<setprecision(x)
#define test int t; cin >> t; while(t--)
#define ff first
#define ss second
#define all(x) x.begin(),x.end()
#define pi 3.14159265358979323846264338327950288419716939937510
#define mset(x) memset(x,0,sizeof x);
#define mset_(x,y) memset(x,y,sizeof x);
#define spa cout<<endd
#define com(x)#x
#define debug false
#define MAX (int)1e9
#define MIN (int)-1e9
//#define modexp
ll inf = 1e18;
ll mod = 1e9 + 7 ;
ll gcd(ll a , ll b){return b==0?a:gcd(b,a%b);}
#ifdef modexp
ll power(ll a , ll b,ll modi)
{
    ll res = 1 ;
    while(b)
    {
        if(b%2) {
            res = (res * a) % modi ;
        }
        b/=2 ;
        a = (a*a) % modi ;
    }
    return res ;
}
#endif
int dirx[] = { -1, -1, -1, 0, 0, 1, 1, 1 };
int diry[] = { -1, 0, 1, -1, 1, -1, 0, 1 };
int dx[]={-1,0,1,0};
int dy[]={0,-1,0,1};


int main()
{
	ll n;
	cin>>n;
    ll a[n+1];
	ll b[n+1];
	ll c[n+1];
	a[0]=b[0]=c[0]=0;
	FOR(i,1,n)
	{
		cin>>a[i];
		{
			b[i]=b[i-1]+a[i];
			c[i]=c[i-1]+(a[i]*a[i]);
		}
	}
	ll ans=0;
	FOR(i,1,n-1)
	{
		FOR(j,i,n-1)
		{
		  ans=max(ans,((b[j]-b[i-1])*(b[j]-b[i-1])-(c[j]-c[i-1]))/2);
		}
	}
	cout<<ans;
}