#!/bin/python3

import sys
from itertools import combinations

def get_cont_sub(A, i):
    for start in range(0, len(A)-i):
        yield A[start:start+i]

def largestValue(A):
    # Return the largest value of any of A's nonempty subarrays.
    best = 0
    for j in range(2, len(A)):
        for a in get_cont_sub(A, j):
            summ = 0
            for i in combinations(a, 2):
                summ += i[0] * i[1]
            if(summ > best):
                best = summ
                
    return best
    
if __name__ == "__main__":
    n = int(input().strip())
    A = list(map(int, input().strip().split(' ')))
    result = largestValue(A)
    print(result)