#!/bin/python3

import sys
import itertools 

def largestValue(A):
    # Return the largest value of any of A's nonempty subarrays.
    largest_val = -999999
    for i in range(len(A)-1):
        for j in range(i+1,len(A)):
            if(arrayValue(A[i:j])>largest_val):
                largest_val = arrayValue(A[i:j])
                
    return largest_val

def arrayValue(A):
    l = []
    pos = 0
    for i in range(len(A)-1):
        for j in range(i+1,len(A)):
            l.append((A[i],A[j]))
    
    return sum([i*j for i,j in l])
    
if __name__ == "__main__":
    n = int(input().strip())
    A = list(map(int, input().strip().split(' ')))
    result = largestValue(A)
    print(result)