import itertools

def max_val_contiguous_subsequence_idxs(seq):
    i = thisSum = maxSum = 0
    startIdx, endIdx = 0, -1
    for j in range(len(seq)):
        thisSum += seq[j]
        if thisSum > maxSum:
            maxSum = thisSum
            startIdx = i
            endIdx   = j
        elif thisSum < 0:
            thisSum = 0
            i = j + 1
    return (maxSum, startIdx, endIdx)



n=int(input())
l=[int(i) for i in input().split()]
maxSum, startIdx, endIdx = max_val_contiguous_subsequence_idxs(l)

l = l[startIdx:endIdx+1]

maximum =0

for subset in itertools.combinations(l, 2):
      maximum = maximum + (subset[0] * subset[1])
print(maximum)