#!/bin/python

import sys

def largestValue(A):
    # Return the largest value of any of A's nonempty subarrays.
    sum_prod = 0
    
    for i in range(0, len(A)):
        for j in range(i+1, len(A)):
            sum_prod += A[i]*A[j]
            
    leftid = 0
    max_left = sum_prod
    curr_sum = sum_prod
    for i in range(0, len(A)-1):
        for j in range(i+1, len(A)):
            curr_sum -= A[i]*A[j]
        if (max_left < curr_sum):
            leftid = i+1
            max_left = curr_sum
    curr_sum = max_left
        
    i = len(A)-1
    rightid = i
    while i > leftid:
        for j in range(leftid, i):
            curr_sum -= A[i]*A[j]
        if (max_left < curr_sum):
            max_left = curr_sum
            rightid = i-1
        i -= 1
        
    return max_left

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