#!/bin/python3

import sys
def arr_val(A):
    n=len(A)
    v=0
    for i in range(n):
        for j in set(A[i+1:]):
            v+=A[i]*j
    return v
def largestValue(A):
    # Return the largest value of any of A's nonempty subarrays.
    n=len(A)
    res=float('-inf')
    for i in range(n):
        for j in range(i+1,n):
            val=arr_val(A[i:j+1])
            if val>res:
                res=val
    return res                

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