#!/bin/python

import sys
import itertools

def value(A):
    total = 0
    for x in itertools.combinations(A, 2):
        total = total + x[0] * x[1]
    return total

def largestValue(A):
    # Return the largest value of any of A's nonempty subarrays.
    maximum = 0
    for first in xrange(len(A)):
        if A[first] > 0:
            for last in xrange(first + 2, len(A)):
                if A[last] < 0:
                    temp = value(A[first:last])
                    if temp > maximum:
                        maximum = temp
    return maximum
        

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