#!/bin/python

import sys

def largestValue(A):
    max_ending_here = 0
    max_so_far = 0
    beg = 0
    for i in xrange(len(A)):
        max_ending_here = max_ending_here + A[i]
        if (max_ending_here < 0):
            max_ending_here = 0
            beg = i + 1
        if (max_so_far < max_ending_here):
            max_so_far = max_ending_here
            start = beg
            end = i+1
    p = 0
    for i in xrange(beg, end):
        for j in xrange(i+1, end):
            p += (A[i]*A[j])
    return p       
        

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