#include <iostream>
#include <fstream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <cmath>
#include <cstring>
#include <unordered_set>
#include <unordered_map>
using namespace std;

#define pb push_back
#define fst first
#define snd second

typedef long long ll;
typedef pair<int,int> pii;
template<typename T> using min_queue=priority_queue<T,vector<T>,greater<T> >;

const ll MOD=1e9+7;

int N;
ll a[500100];
ll s1[500100];
ll s2[500100];

int main(){
  ios::sync_with_stdio(0);cin.tie(0);

  cin>>N;
  for(int i=1;i<=N;i++){
    cin>>a[i];
    s1[i]=s1[i-1]+a[i];
    s2[i]=s2[i-1]+a[i]*a[i];
  }

  ll best=0;
  for(int i=0;i<=N;i++){
    for(int j=i+1;j<=N;j++){
      best=max(best,((s1[j]-s1[i])*(s1[j]-s1[i])-(s2[j]-s2[i]))/2);
    }
  }

  cout<<best<<'\n';

  return 0;
}