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

typedef vector<int> vi;
typedef pair<int, int> ii;
typedef long long ll;
typedef pair<long long, long long> l4;
typedef vector<long long> vll;
typedef double db;
typedef vector<double> vdb;
typedef pair<double, double> dd;
typedef set<int> si;
typedef set<long long> sll;
#define fi first
#define se second
#define matrix(a) vector< vector<a> >
#define sz(a) int((a).size()) 
#define lop(i,a,b) for (int i=a; i<=b; i++)
#define rlop(i,a,b) for (int i=b; i>=a; i--)
#define all(s) (s).begin(),(s).end()
#define pb push_back
#define enter cout<<'\n'
#define lb(i,v) int(lower_bound(all(v),i)-v.begin())
#define ub(i,v) int(upper_bound(all(v),i)-v.begin())

int main() {
    int n;
    cin >> n;
    vll a(n);
    for(int A_i = 0; A_i < n; A_i++){
       cin >> a[A_i];
    }
    vll sum(n),sqsum(n);
    sum[0]=a[0];
    sqsum[0]=a[0]*a[0];
    lop(i,1,n-1){
        sum[i]=sum[i-1]+a[i];
        sqsum[i]=sqsum[i-1]+a[i]*a[i];
    }
    ll ans=0;
    lop(i,0,n-2){
        lop(j,i+1,n-1){
            ll s,p;
            if(!i){
                s=sum[j];
                p=sqsum[j];
            }
            else{
                s=sum[j]-sum[i-1];
                p=sqsum[j]-sqsum[i-1];
            }
            ans=max(ans,s*s-p);
        }
    }
    cout<<ans/2;
    return 0;
}