#!/bin/python3

import sys
def largestValue(A):
    max1= max(A)
    n = len(A)
    for i in range(2,n+1):
        for j in range(n-i+1):
            temp = A[j:j+i]
            temp1 = 0
            for k in range(len(temp)):
                for l in range(k+1,len(temp)):
                    temp1+=(temp[k]*temp[l])
            if temp1>max1:
                max1 = temp1
    return max1           
                
            
    
    # Return the largest value of any of A's nonempty subarrays.

if __name__ == "__main__":
    n = int(input().strip())
    A = list(map(int, input().strip().split(' ')))
    result = largestValue(A)
    print(result)