#!/bin/python3

import sys

def largestValue(A):
    # Return the largest value of any of A's nonempty subarrays.
    largestval = -10**8
    n = len(A)
    for i in range(n-1):
        sm = A[i]
        pr = 0
        for j in range(i+1,n):
            pr += sm*A[j]
            sm += A[j]
            #print(pr)
            if pr > largestval:
                largestval = pr
                
    return largestval

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