"""Brute force"""
#!/bin/python3

import sys

def largestValue(A):
    # Return the largest value of any of A's nonempty subarrays.
    n = len(A)
    best = 0
    for i in range(n):
        cursum = A[i]
        curval = 0
        for j in range(i+1, n):
            curval += A[j] * cursum
            if curval > best:
                best = curval
            cursum += A[j]
    return best

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