#include<bits/stdc++.h>

#define X first
#define Y second
#define eb push_back
#define siz(a) int(a.size())
#define endl "\n"

#define trace2(x, y)             cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<< endl;
#define trace3(x, y, z)          cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<endl;
#define trace4(a, b, c, d)       cout <<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<endl;
#define trace5(a, b, c, d, e)    cout <<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<" | "<<#e<<": "<<e<<endl;

using namespace std;

typedef int ll;
typedef vector < int > vi;
typedef vector < ll > vll;

const int mod=1e9+7;
const int maxn=5555;

/*	finding inverse upto n
 * for i in xrange(2, N):
    ifc[i] = -(mod / i) * ifc[mod % i] % mod
 * 
*/
ll power(ll base, ll exp){ll res = 1; while(exp){if(exp%2)res*=base;base*=base;res%=mod;base%=mod;exp/=2;}return res;}

ll arr[maxn], sum[maxn][maxn], pre[maxn], up[maxn][maxn];

ll calc(ll y, ll x){
	ll ans = 0;
	for(ll i =y; i<=x; i++){
		for(ll j = i+1; j<=x; j++)
			ans += arr[i]*arr[j];
	}
	return ans;
}

int main(){
	ios_base::sync_with_stdio(false);cin.tie(NULL); cout.tie(NULL);
	//freopen("input.in", "r", stdin);freopen("output.out", "w", stdout);	
	ll n, i;
	cin >> n;
	
	for(i=1; i<=n; i++)
		 cin >> arr[i];
	
	ll ans = -1e17, curr = 0;
	ll j;
	for(i=1; i<=n; i++){
		for(j=i+1; j<=n; j++){
			sum[i][j] += arr[i]*arr[j] + sum[i][j-1];
			
			pre[j] += sum[i][j];
			
		//	trace4(i, j, sum[i][j], pre[j]);
		}
	}
	
	for(j=1; j<=n; j++)
		for(i=1; i<=n; i++)
			up[i][j] += up[i-1][j] + sum[i][j];
	
	//for(i=1; i<=n; i++)
		//trace3(i, pre[i], calc(i));
	
	for(i=1; i<=n; i++){
		for(j=i+1; j<=n; j++){
			ans = max(ans, pre[j] - up[i-1][j]);
			
//			trace5(i, j, calc(i, j), pre[j] - up[i-1][j], ans);
		}
		
	}
	
	cout << ans;
	
	return 0;
}