#include <bits/stdc++.h>

using namespace std;

long largestValue(vector <int> a) 
{
  long n=a.size(),i;
  long  dp[n]={0};
  long sum[n],prev=0,maxi=0;  
  // Dp state is i,j
   // i is start index
  //  j is length is subarray- we can compute end index
   
   for(i=0;i<n;i++)
   {
      sum[i]=a[i]+prev;
      prev=sum[i];
   //    cout<<sum[i]<<" ";
   }   
  //  cout<<endl;
    dp[n-1]=a[n-2]*a[n-1];
    maxi=dp[n-1];
  
  /*  for(i=n-3;i>=0;i--)
    {dp[i][i+1]=a[i]*a[i+1]; // base case
      maxi=max(maxi,dp[i][i+1]);
    }
    */
    
   long j;// k used fr length
    
 for(i=n-3;i>=0;i--)
  { dp[i+1]=a[i]*a[i+1];
     for(j=i+2;j<n;j++)
     {
      // cout<<sum[j-1]<<" "<<sum[i]<<" "<<a[i]<<" "<<sum[j]-sum[i]+a[i]<<endl;  
       dp[j]=(sum[j-1]-sum[i]+a[i])*(a[j])+dp[j-1];  
        maxi=max(maxi,dp[j]);
         
         
     }
   } 
   
   /* for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
            cout<<dp[i][j]<<" ";
        cout<<endl;
    }
    */
    return maxi;
    
}

int main() {
    int n;
    cin >> n;
    vector<int> A(n);
    for(int A_i = 0; A_i < n; A_i++){
       cin >> A[A_i];
    }
    long result = largestValue(A);
    cout << result << endl;
    return 0;
}