#include <bits/stdc++.h>

//#define DEBUG 1

//#define int long long
#define for0(i,n) for (int i=0; i<n; i++)
#define iter(c) for(auto it=c.begin(); it!=c.end(); it++)
#define iter2(c) for(auto it2=c.begin(); it2!=c.end(); it2++)
#define pb push_back
#define ms(a,z) memset(a,z,sizeof(a));
#define mp make_pair
#define X first
#define Y second
#define max(a,b) ((a)>(b)?(a):(b))
#define min(a,b) ((a)<(b)?(a):(b))
#define all(a) a.begin(),a.end()
#define sz(x) (int)(x).size()
#define pmod(x,m) (((x)%(m)+m)%m)
#ifdef int
#define read(x) scanf("%lld",&x);
#else
#define read(x) scanf("%d",&x);
#endif

#ifdef DEBUG
#define nl cout<<"\n";
#define pr(x) cout<<(x)<<" ";
#define prl(x) cout<<#x " = "<<x<<endl;
#define prp(x) cout<<"("<<(x).first<<" "<<(x).second<<") ";
#define printv(v) {for(int _=0; _<sz(v); _++) cout<<v[_]<<" "; cout<<"\n";}
#define printa(a,s) {for (int _=0; _<s; _++) cout<<a[_]<<" "; cout<<"\n";}
#define print2D(a,m,n) {for (int _=0; _<m; _++) {for (int __=0; __<n; __++) cout<<a[_][__]<<" "; cout<<"\n";} cout<<"\n";}
#define priter(v) iter(v) {pr(*it)} nl
#define debug cout<<"ok at line "<<__LINE__<<endl;
#else
#define nl
#define pr(x)
#define prl(x)
#define prp(x)
#define printv(v)
#define printa(a,s)
#define print2D(a,m,n)
#define priter(v)
#define debug
#endif
#define MAXN 5000

using namespace std;

typedef long long ll;

const int INF = 2147483647;
const long long INFL = 9223372036854775807LL;
const double EPSILON = 0.00000001;
const long long MOD = 1000000007;

ll a[MAXN+5];
ll suba_sums[MAXN+5][MAXN+5];
ll suba_vals[MAXN+5][MAXN+5];

int32_t main()
{
    #ifdef DEBUG
    //freopen("C.txt","r",stdin);
    //freopen("","w",stdout);
    #endif

    int n;
    cin >> n;
    for0(i,n) {
        //read(a[i]);
        scanf("%lld",&a[i]);
    }
    printa(a,n);
    
    ms(suba_sums,0);
    ms(suba_vals,0);
    for0(i,n) {
        suba_sums[i][i] = a[i];
        suba_vals[i][i] = 0;
    }
    ll best = 0;
    for (int l=2; l<=n; l++) {        
        for (int i=0; i<n; i++) {
            int j = i+l-1;
            if (j >= n)
                continue;
            suba_sums[i][j] = a[j] + suba_sums[i][j-1];
            suba_vals[i][j] = suba_vals[i][j-1] + a[j]*suba_sums[i][j-1];
            best = max(best,suba_vals[i][j]);
        }
    }
    print2D(suba_sums,n+1,n+1);
    print2D(suba_vals,n+1,n+1);
    
    cout<<best<<endl;
    return 0;
}