#!/bin/python3

import sys
import itertools

def largestValue(A):
    vmax = -1000000

    for i in range(0,len(A)):
        for j in range(1,len(A)-i+1):
            c = A[i:i+j]
            x = list(itertools.combinations(c,2))
            tot = 0
            for item in x:
                tot += item[0] * item[1]
            if (tot > vmax):
                vmax = tot
    return vmax;


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