백준-1744

N = int(input())
pos = []
neg = []

for i in range(N):
  k = int(input())
  if k > 0:
    pos.append(k)
  else:
    neg.append(k)

pos.sort(reverse=True)
neg.sort()
sur = pos.count(1)
for i in range(sur):
  pos.remove(1)

zeros = neg.count(0)
for i in range(zeros - 1):
  neg.remove(0)

def iteration(lst):
  ret = 0
  while len(lst) > 1:
    ret += lst[0] * lst[1]
    lst.pop(0)
    lst.pop(0)
  if len(lst) == 1:
    ret += lst.pop()
  return ret

print(iteration(pos) + iteration(neg)+ sur)