#!/bin/python3

import sys

def largestValue(A):
    n=len(A)-1
    m=0
    while(n>=2):
        for i in range(0,len(A)-n+1):
            a=list(A[j] for j in range(i,n+i))
            s=0
            for j in range(len(a)-1):
                s+=a[j]*sum(a[j+1:])
            if(m<s):
                m=s
        n-=1
    return m
    

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