#!/bin/python3

import sys

def largestValue(A):
    sum_p=0
    l=len(A);
    for i in range(0,l):
        for j in range(i+1,l):
            sum_p=sum_p+(A[i]*A[j])
    return sum_p 
def sub_array_max(A):
    l=[]
    
    max_value=0
    for i in range(0,len(A)):
        j=len(A)-1
        while j>=0:
            l=A[i:j]
            if(largestValue(l))>max_value:
                m=l;
                max_value=largestValue(l)
            j=j-1    
    return max_value            

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