#!/bin/python3

import sys

def calculate(N):
    r = 0
    s = sum(N)
    for e in N:
        s -= e
        r += s * e
    return r

def largestValue(A):
    cal = 0
    for i in range(len(A) - 1):
        for j in range(len(A[i:]) - 1):
            #print(A[i:i+j+2])
            t = calculate(A[i:i+j+2])
            if (cal < t):
                cal = t
    return cal
    # Return the largest value of any of A's nonempty subarrays.

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