n = int(input())
a = list(map(int, input().split(" ")))

a.sort(reverse=True)

happiness = 0

if n <= 200000:
  for i in range(n):
    if n % 2 == 0:
      if i + 1 <= n // 2 and a[i] >= 0:
        happiness += a[i]
    else:
      if i + 1 <= n // 2 + 1 and a[i] >= 0:
        happiness += a[i]