#!/bin/python3

import sys

def largestValue(A):
    if len(A) == 1:
        return A[0]
    if A[0] < 0:
        return largestValue(A[1:])
    if A[-1] < 0:
        return largestValue(A[:-1])
    sum_left = 0
    sum_right = 0
    for i, el in enumerate(A):
        if i != 0:
            sum_right += A[-1]*A[i]
        if i != (len(A) - 1):
            sum_left += A[0]*A[i]
    if sum_left < 0:
        return largestValue(A[1:])
    if sum_right < 0:
        return largestValue(A[:-1])
    sum_ = 0
    for i, el1 in enumerate(A):
        for j in range(i+1,len(A)):
            sum_ += A[i] * A[j]
    return sum_
    
    
if __name__ == "__main__":
    n = int(input().strip())
    A = list(map(int, input().strip().split(' ')))
    result = largestValue(A)
    print(result)