n = int(input())
a = [ int(i) for i in input().split() ]

ans = -1000000000
for i in range(0,n):
    for j in range(i+1,n):
        cur = a[i:j+1]
        cur_n = len(cur)
        su = 0
        for x in range(0,cur_n):
            for y in range(x+1,cur_n):
                su += cur[x]*cur[y] 
        if su > ans:
            ans = su
            
print(ans)