#!/bin/python3

import sys

def mul(A):
    summe = 0
    for i in range(len(A)):
        for j in range(i + 1, len(A)):
            summe += (A[i] * A[j])
    return summe

def largestValue(A):
    maxSumme = 0
    for i in range(len(A)):
        s = mul(A[i:])
        if s > maxSumme: maxSumme = s
        s = mul(A[:len(A) - i])
        if s > maxSumme: maxSumme = s
        s = mul(A[i:len(A) - i])
        if s > maxSumme: maxSumme = s
        s = mul(A[i - 1:len(A) - i])
        if s > maxSumme: maxSumme = s
        s = mul(A[i:len(A) - i + 1])
        if s > maxSumme: maxSumme = s
    return maxSumme

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