#!/bin/python

import sys

def getpos(A):
    j=0
    for i in xrange(0,len(A)):
        if A[i]<0:
            j=i+1
        else:
            return j
    return j

def multiply(V,a):
    prod=0
    for i in V:
        prod+=a*i
    return prod
    
def largestValue(A):
    V=[]
    i=getpos(A)
    start=i
    summ=0
    sum_=0
    cand=-1
    fin=0
    for i in xrange(i,len(A)):
        if(cand!=-1):
            if(A[i]<0):
                cand=i
                V.append(A[i])
                summ=A[i]
                sum_=A[i]
        else: #cand=-1
                sum_+=multiply(V,A[i])
                if(sum_>summ):
                    cand=-1
                    summ=0
                    sum_=0
                    V=[]
    if cand==-1:
        cand=len(A)-1
    sum=0
    for i in xrange(i,cand):
        for j in xrange(i+1,cand+1):
            sum += multiply(V[i:j-1],A[j])
    
    return sum
    # Return the largest value of any of A's nonempty subarrays.

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