#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include  <cstdlib>
#include <cstring>
using namespace std;
#define ll long long
ll maxSubArraySum(int a[], int size)
{
   ll max_so_far = 0, max_ending_here = 0;
   for (int i = 0; i < size; i++)
   {
       max_ending_here = max_ending_here + a[i];
       if (max_ending_here < 0)
           max_ending_here = 0;
       else if (max_so_far < max_ending_here)
           max_so_far = max_ending_here;
   }
   return max_so_far;
}

int main() {
    int n;
    cin >> n;
    int arr[n];
    for(int i=0;i<n;i++) cin >>arr[i];
    int a2[2*n];
    memset(a2,0,sizeof(a2));
    int k=0;
    for(int i=0;i<n;i++)
    {
        for(int j=i+1;j<n;j++)
            a2[k++]=arr[i]*arr[j];
    }
    
    //for(int i=0;i<2*n;i++) cout <<a2[i]<<"\t";
    ll p=maxSubArraySum(a2,n);
    cout<<p<<"\n";
    
}