# pragma GCC optimize("O3")
# include <bits/stdc++.h>
std::pair<int,int> DR[] = {{-1,0},{0,1},{1,0},{0,-1},{-1,1},{-1,-1},{1,1},{1,-1}};
# define ll long long
# define clock (clock() * 1000.0 / CLOCKS_PER_SEC)
# define rc(s) return cout << s,0
# define _ ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
# define db(x) cerr << #x << " = " << x << '\n'
# define pb push_back
# define mp make_pair
# define all(s) s.begin(),s.end()
# define sz(x) (int)((x).size())
# define int ll
using namespace std;

int n,a[1 << 20],ans;

int32_t main(){_
    //freopen("input","r",stdin);
    cin >> n;
    for(int i = 1;i <= n;i++)
    {
        cin >> a[i];
    }
    if(n <= 5000){
    for(int i = 1;i <= n;i++)
    {
        int sum = 0;
        int x = 0;
        for(int j = i;j <= n;j++)
        {
            x += a[j] * sum;
            sum += a[j];
            ans = max(ans,x);
        } 
    }
    }
    else
    {
        while(clock < 1000)
        {
            int b = rand() % n;
            b++;
            int sum = 0;
            int x = 0;
            for(int j = b;j <= n;j++)
            {
            x += a[j] * sum;
            sum += a[j];
            ans = max(ans,x);
            } 
        }
        rc(ans);
    }
    rc(ans);
}