#!/bin/python3

import sys
def largestValue(A):
    l=[0]*(n+1)
    l2=[0]*(n+1)
    l[1]=A[0]
    l2[1]=A[0]**2
    for i in range(1,n+1):
        l[i]=l[i-1]+A[i-1]
        l2[i]=l2[i-1]+A[i-1]**2
    curr=0
    for i in range(n-1):
        for j in range(i+1,n):
            v=l[j+1]-l[i]
            v2=l2[j+1]-l2[i]
            w=(v**2-v2)//2
            if curr < w:
                curr=w
    return curr

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